[TS/JS] New gen TS code gen (#6302)

* TS/ES6 modules spike iteration 1

* Initial modularized dasherized output

* Remove obsoleted parts and namespace wrapping

* Use _flatbuffers_ prefix

* First part of imports logic

* Second part of imports logic

* Fix TS/JS code removal mixup

* Alias imported symbols if same name from different namespaces and some fixes

* Use star import for bare imports

* Fix messed up string concat

* var to const and remove not needed semi

* Remove some cases of ns prefixing

* Add missing space

* Cleanups

* Completed initial import tracking logic

* Compilable output

* Adjust TypeScriptTest and dependents to work

* Use local flatbuffers package for tests

* Refactor away use of any

* Remove obsolete imported_fileset and reexport_map

* Still need any and fix JavaScriptTest.sh

* Fix test runs out of the box

* Temp add generated files

* TypeScriptTest replaces JavaScriptTest and cleanups

* Also remove reference to JavaScriptTest in TestAll.sh

* Remove old generated ts/js files

* Remove use of --js in generate_code scripts

* idl_gen_js_ts to idl_gen_ts and removal of js gen

* Remove obsoleted options

* Fix obsolete ts test detection

* Tweak ts compilation be as strict as possible

* Remove jsdoc type annotation generation

* Generated test ts files

* Fix search and replace messup

* Regenerated ts test output

* Use CharToLower

* Use normal for loop

* Rework namespacedir

* Revert "Rework namespacedir"

This reverts commit 6f4eb0104ceeb86011bb076ebca901138c48e068.

* Revert "Use normal for loop"

This reverts commit 676b2135bfaa1853dfbb06c92b5c16a0d81bb13a.

* Revert "Use CharToLower"

This reverts commit 2d08648d0d72d0af201fad80d54cdc76412b35e9.

* Again do rework but correct

* Avoid runtime cast

* Fix test runs

* Also add npm install to get tsc

* Bump node test versions

* for range to std for loop

* Clang format

* Missed one clang format

* Move accessor to later

* Attempt to make windows version of TypeScriptTest

* Want to see the output

* Try to get newer node at appveyor

* Style changes

package.json

@@ -16,11 +16,9 @@
     "test": "tests"
   },
   "scripts": {
-    "test": "cd tests && ./JavaScriptTest.sh",
-    "compile-ts": "tsc && tsc -p tsconfig.mjs.json",
-    "pretest": "npm run compile-ts",
-    "append-esm-export": "sed \"s/this.flatbuffers = flatbuffers;/export { flatbuffers };/\" js/flatbuffers.js > js/flatbuffers.mjs",
-    "prepublishOnly": "npm run compile-ts && npm run append-esm-export"
+    "test": "npm run compile && cd tests && ./TypeScriptTest.sh",
+    "compile": "tsc && tsc -p tsconfig.mjs.json",
+    "prepublishOnly": "npm run compile"
   },
   "repository": {
     "type": "git",
@@ -37,9 +35,9 @@
   "homepage": "https://google.github.io/flatbuffers/",
   "dependencies": {},
   "devDependencies": {
-    "@typescript-eslint/eslint-plugin": "^4.1.0",
-    "@typescript-eslint/parser": "^4.1.0",
-    "eslint": "^7.8.1",
-    "typescript": "^4.0.2"
+    "@typescript-eslint/eslint-plugin": "^4.12.0",
+    "@typescript-eslint/parser": "^4.12.0",
+    "eslint": "^7.17.0",
+    "typescript": "^4.1.3"
   }
 }