feat(stdlib): Add `forEachChar`, `forEachCharI`, `map` and `mapi` to String module #8476

Job	Run time
Build and test on windows-latest / Dependencies / Create dependencies cache	58m 1s
Build and test on ubuntu-latest / Dependencies / Create dependencies cache	26m 56s
Build and test on macos-latest / Dependencies / Create dependencies cache	39m 46s
Build and test on ubuntu-latest / (js) Build and test / (js) Build and test	22m 10s
Build and test on ubuntu-latest / (native) Build and test / (native) Build and test	7m 58s
Build and test on macos-latest / (native) Build and test / (native) Build and test	12m 32s
Build and test on macos-latest / (js) Build and test / (js) Build and test	12m 48s
Build and test on windows-latest / (native) Build and test / (native) Build and test	15m 25s
Build and test on windows-latest / (js) Build and test / (js) Build and test	36m 27s
Test pkg binaries	0s
	3h 52m 3s

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