generator: implement generator for builtin go types

* supported optional types are int*, uint*, float*, bytes, string, bool
* fully redo configuration for golangci-lint
* simple tests for encoding/decoding roundtrip

Closes #TNTP-3729

Author: bigbes

.golangci.yml

@@ -8,22 +8,50 @@ formatters:
     - goimports
 
 linters:
-  enable:
-    - forbidigo
-    - gocritic
-    - lll
-    - reassign
-    - unconvert
-    - gosec
-    - errorlint
-    - godot
-    - revive
-    - testpackage
-    - unused
+  default: all
+
+  disable:
+    - dupl     # Dupl is disabled, since we're generating a lot of boilerplate code.
+    - cyclop   # Cyclop is disabled, since cyclomatic complexities is very abstract metric,
+               # that sometimes lead to strange linter behaviour.
+    - wsl      # WSL is disabled, since it's obsolete. Using WSL_v5.
+    - nlreturn # nlreturn is disabled, since it's duplicated by wsl_v5.return check.
+    - ireturn  # ireturn is disabled, since it's not needed.
+
+  exclusions:
+    rules:
+      - path-except: cmd/generator/*.go
+        linters:
+        - forbidigo        # fmt functions are not forbidden here
+        - gochecknoglobals # global variables are not forbidden here
 
   settings:
     godot:
       scope: all
     lll:
       line-length: 120
       tab-width: 4
+    wsl_v5:
+      allow-first-in-block: true
+      allow-whole-block: false
+      branch-max-lines: 2
+      case-max-lines: 0
+      default: all
+    depguard:
+      rules:
+        main:
+          files:
+            - "$all"
+            - "!$test"
+          allow:
+            - $gostd
+            - "github.com/vmihailenco/msgpack/v5"
+            - "golang.org/x/text"
+        test:
+          files:
+            - "$test"
+          allow:
+            - $gostd
+            - "github.com/stretchr/testify"
+            - "github.com/vmihailenco/msgpack/v5"
+            - "github.com/tarantool/go-option"

CHANGELOG.md

@@ -10,6 +10,10 @@ Versioning](http://semver.org/spec/v2.0.0.html) except to the first release.
 
 ### Added
 
+- Implemented optional types for builtin go types int*, uint*, float*,
+  bytes, string, bool.
+
+
 ### Changed
 
 ### Fixed