Move Core into compiler repo (#7108)

* Add Core sources

* Remove @rescript/core from playground bundle

* Move ocaml compat modules into tests

* Remove Core__ prefix from file names

* Remove Core__ prefix from module names

* make artifacts

* __ -> _

* Fix tests

* Add Array.unsafe_get for compatibility

* CHANGELOG

* Improve cleaning in runtime build script

* Js_exn -> Exn

* Move Core Global into Pervasives

CHANGELOG.md

@@ -23,7 +23,8 @@
 - Use FORCE_COLOR environmental variable to force colorized output https://github.com/rescript-lang/rescript-compiler/pull/7033
 - Allow spreads of variants in patterns (`| ...someVariant as v => `) when the variant spread is a subtype of the variant matched on. https://github.com/rescript-lang/rescript-compiler/pull/6721
 - Fix the issue where dynamic imports are not working for function-defined externals. https://github.com/rescript-lang/rescript-compiler/pull/7060 
-- Allow pattern matching on dicts. `switch someDict { | dict{"one": 1} => Js.log("one is one") }` https://github.com/rescript-lang/rescript-compiler/pull/7059
+- Allow pattern matching on dicts. `switch someDict { | dict{"one": 1} => Js.log("one is one") }`. https://github.com/rescript-lang/rescript-compiler/pull/7059
+- "ReScript Core" standard library is now included in the `rescript` npm package. https://github.com/rescript-lang/rescript-compiler/pull/7108
 
 #### :bug: Bug fix