JavaScript: make bytes literals use Uint8Array (not number[])

Until now, byte array literals translated for JavaScript were of type
`number[]`, as TypeScript would call this type (in pure JS terminology,
it's an `Array` object with numbers). For example, a value instance
defined as `instances/v/value: '[65, 126]'` would be translated as
`this._m_v = [65, 126];` in the generated JS code. However, byte arrays
created in any other way would use the
[`Uint8Array`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array)
type, which is the standard type for byte arrays in JavaScript. Namely
any byte array parsed from stream would be a `Uint8Array` object and
also a *non-literal* byte array like `[123, 246 + 0].as<bytes>` would be
generated as `new Uint8Array([123, 246 + 0])`.

I believe that using a different type for byte array literals than for
byte arrays created in any other way was never intentional. It seems we
simply forgot to override `doByteArrayLiteral` in `JavaScriptTranslator`
(but `doByteArrayNonLiteral` is overridden correctly, which is weird),
so we ended up using the default `BaseTranslator.doByteArrayLiteral`
implementation, which produces the `[65, 126]` syntax.

JavaScript is dynamically typed, so you can treat `number[]` the same as
`Uint8Array` in most cases (e.g. indexing will work the same), but this
discrepancy now causes problems when porting our JavaScript runtime
library to TypeScript (see
kaitai-io/kaitai_struct_javascript_runtime#25),
because you would have to annotate a lot of parameter types as `number[]
| Uint8Array` (which doesn't really make sense). Moreover, I discovered
that generating byte array literals as `number[]` creates a bug in this
case:

```ksy
meta:
  id: bytes_to_s
instances:
  literal:
    value: '[65, 126].to_s("UTF-8")'
```

Before this commit, `[65, 126].to_s("UTF-8")` would be translated as
`KaitaiStream.bytesToStr([65, 126], "UTF-8")` for JavaScript. But our
`bytesToStr` implementation won't actually accept `number[]` for
non-ASCII encodings. See
[`KaitaiStream.js:650-657`](https://github.com/kaitai-io/kaitai_struct_javascript_runtime/blob/2acb0d8b09fde9c95fc77ee3019f6d6b1c73f040/KaitaiStream.js#L650-L657):

```js
KaitaiStream.bytesToStr = function(arr, encoding) {
  if (encoding == null || encoding.toLowerCase() === "ascii") {
    return KaitaiStream.createStringFromArray(arr);
  } else {
    if (typeof TextDecoder === 'function') {
      // we're in the browser that supports TextDecoder
      return (new TextDecoder(encoding)).decode(arr);
    } else {
```

If `TextDecoder` is available (which is the case in a browser or since
Node.js 11), the error when trying to access the `literal` instance
above will look like this in the browser (Google Chrome 129):

```
TypeError: Failed to execute 'decode' on 'TextDecoder': parameter 1 is not of type 'ArrayBuffer'.
    at KaitaiStream.bytesToStr (https://ide.kaitai.io/devel/lib/_npm/kaitai-struct/KaitaiStream.js:656:42)
    at BytesToS.get (eval at initCode (https://ide.kaitai.io/devel/js/v1/kaitaiWorker.js:156:9), <anonymous>:27:38)
    at fetchInstance (https://ide.kaitai.io/devel/js/v1/kaitaiWorker.js:123:20)
    ...
```

... and like this in Node.js 12:

```
TypeError [ERR_INVALID_ARG_TYPE]: The "input" argument must be an instance of ArrayBuffer or ArrayBufferView. Received an instance of Array
    at TextDecoder.decode (internal/encoding.js:412:15)
    at Function.KaitaiStream.bytesToStr (/runtime/javascript/KaitaiStream.js:656:42)
    at BytesToS.get (compiled/javascript/BytesToS.js:26:38)
    at /tests/spec/javascript/test_bytes_to_s.js:8:24
    ...
```

So using `Uint8Array` for all byte arrays will not only be more
consistent, but will also fix this bug.

Author: generalmimon

jvm/src/test/scala/io/kaitai/struct/translators/TranslatorSpec.scala

@@ -406,7 +406,7 @@ class TranslatorSpec extends AnyFunSpec {
         CSharpCompiler -> "new byte[] { 34, 0, 10, 64, 65, 66, 92 }",
         GoCompiler -> "[]uint8{34, 0, 10, 64, 65, 66, 92}",
         JavaCompiler -> "new byte[] { 34, 0, 10, 64, 65, 66, 92 }",
-        JavaScriptCompiler -> "[34, 0, 10, 64, 65, 66, 92]",
+        JavaScriptCompiler -> "new Uint8Array([34, 0, 10, 64, 65, 66, 92])",
         LuaCompiler -> "\"\\034\\000\\010\\064\\065\\066\\092\"",
         PerlCompiler -> "pack('C*', (34, 0, 10, 64, 65, 66, 92))",
         PHPCompiler -> "\"\\x22\\x00\\x0A\\x40\\x41\\x42\\x5C\"",
@@ -419,7 +419,7 @@ class TranslatorSpec extends AnyFunSpec {
         CSharpCompiler -> "new byte[] { 255, 0, 255 }",
         GoCompiler -> "[]uint8{255, 0, 255}",
         JavaCompiler -> "new byte[] { -1, 0, -1 }",
-        JavaScriptCompiler -> "[255, 0, 255]",
+        JavaScriptCompiler -> "new Uint8Array([255, 0, 255])",
         LuaCompiler -> "\"\\255\\000\\255\"",
         PerlCompiler -> "pack('C*', (255, 0, 255))",
         PHPCompiler -> "\"\\xFF\\x00\\xFF\"",
@@ -434,7 +434,7 @@ class TranslatorSpec extends AnyFunSpec {
         CSharpCompiler -> "new byte[] { 0, 1, 2 }.Length",
         GoCompiler -> "len([]uint8{0, 1, 2})",
         JavaCompiler -> "new byte[] { 0, 1, 2 }.length",
-        JavaScriptCompiler -> "[0, 1, 2].length",
+        JavaScriptCompiler -> "new Uint8Array([0, 1, 2]).length",
         LuaCompiler -> "#\"\\000\\001\\002\"",
         PerlCompiler -> "length(pack('C*', (0, 1, 2)))",
         PHPCompiler -> "strlen(\"\\x00\\x01\\x02\")",
@@ -816,7 +816,7 @@ class TranslatorSpec extends AnyFunSpec {
         CSharpCompiler -> "new byte[] {  }",
         GoCompiler -> "[]uint8{}",
         JavaCompiler -> "new byte[] {  }",
-        JavaScriptCompiler -> "[]",
+        JavaScriptCompiler -> "new Uint8Array([])",
         LuaCompiler -> "\"\"",
         PerlCompiler -> "pack('C*', ())",
         PHPCompiler -> "\"\"",

shared/src/main/scala/io/kaitai/struct/translators/JavaScriptTranslator.scala

@@ -8,6 +8,8 @@ import io.kaitai.struct.format.{EnumSpec, Identifier}
 import io.kaitai.struct.languages.JavaScriptCompiler
 
 class JavaScriptTranslator(provider: TypeProvider, importList: ImportList) extends BaseTranslator(provider) {
+  override def doByteArrayLiteral(arr: Seq[Byte]): String =
+    s"new Uint8Array([${arr.map(_ & 0xff).mkString(", ")}])"
   override def doByteArrayNonLiteral(elts: Seq[Ast.expr]): String =
     s"new Uint8Array([${elts.map(translate).mkString(", ")}])"