feat: initial ESM support (elastic#3381)

This adds initial and ECMAScript Module (ESM) support, i.e. `import ...`,
via the `--experimental-loader=elastic-apm-node/loader.mjs` node option.
This instruments a subset of modules -- more will follow in subsequent changes.

Other changes:
- Fixes a fastify instrumentation issue where the exported `fastify.errorCodes`
  was broken by instrumentation (both CJS and ESM).
- Adds a `runTestFixtures` utility that should be useful for running out of
  process instrumentation/agent tests.

Closes: elastic#1952
Refs: elastic#2343

Author: trentm

.eslintrc.json

@@ -21,6 +21,7 @@
   },
   "ignorePatterns": [
     "/*.example.js", // a pattern for uncommited local dev files to avoid linting
+    "/*.example.mjs", // a pattern for uncommited local dev files to avoid linting
     "/.nyc_output",
     "/build",
     "node_modules",
@@ -40,6 +41,10 @@
     "/test/types/transpile/index.js",
     "/test/types/transpile-default/index.js",
     "/test_output",
-    "tmp"
+    "tmp",
+    // These files use top-level await, which is *fine* for ESM files but, IIUC,
+    // not supported by eslint until v8.
+    "/test/instrumentation/modules/fixtures/use-fastify.mjs",
+    "/test/instrumentation/modules/http/fixtures/use-dynamic-import.mjs"
   ]
 }

.tav.yml

@@ -115,8 +115,7 @@ pg-old-node:
   versions: '4.0.0 || 4.5.7 || 5.2.1 || 6.4.2 || 7.18.2 || 8.0.3 || 8.1.0 || 8.2.2 || 8.3.3 || 8.4.2 || 8.5.1 || 8.6.0 || 8.7.3 || 8.8.0 || 8.9.0 || 8.10.0 || >8.10.0 <9'
   node: '<14'
   peerDependencies:
-    - bluebird@^3.0.0
-    - knex@^0.17.3
+    - knex@^0.20 # latest knex that supports back to node v8
   commands:
     - node test/instrumentation/modules/pg/pg.test.js
     - node test/instrumentation/modules/pg/knex.test.js
@@ -129,9 +128,6 @@ pg-new-node:
   # Maintenance note: This should be updated for newer MAJOR.MINOR releases.
   versions: '8.0.3 || 8.1.0 || 8.2.2 || 8.3.3 || 8.4.2 || 8.5.1 || 8.6.0 || 8.7.3 || 8.8.0 || 8.9.0 || 8.10.0 || >8.10.0 <9'
   node: '>=14'
-  peerDependencies:
-    - bluebird@^3.0.0
-    - knex@^0.17.3
   commands:
     - node test/instrumentation/modules/pg/pg.test.js
     - node test/instrumentation/modules/pg/knex.test.js