[PoC]: Add platform-specific module support

[fhammerschmidt]

Adds opt-in platform modules through "platforms": ["android", "ios"]. Files such as Button.android.res and Button.ios.res share Button.resi, compile to platform-specific JavaScript filenames, and are imported through the logical Button module so React Native’s resolver can select the correct implementation.

React Native is only the driving example here but the mechanism is of course fully generic and works with arbitrary platform names.

Fixes #1436

[codecov]

Codecov Report

❌ Patch coverage is 89.74359% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.60%. Comparing base (d90b96a) to head (12749a6).

Files with missing lines	Patch %	Lines
analysis/src/find_files.ml	85.36%	6 Missing ⚠️
compiler/core/lam_stats_export.ml	92.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8637      +/-   ##
==========================================
+ Coverage   77.58%   77.60%   +0.01%     
==========================================
  Files         475      476       +1     
  Lines       64062    64104      +42     
==========================================
+ Hits        49704    49749      +45     
+ Misses      14358    14355       -3     

Files with missing lines	Coverage Δ
analysis/src/packages.ml	76.72% <100.00%> (+0.20%)	⬆️
compiler/bsc/rescript_compiler_main.ml	71.63% <100.00%> (+0.13%)	⬆️
compiler/common/js_config.ml	75.00% <ø> (ø)
compiler/core/js_packages_info.ml	75.00% <100.00%> (+1.08%)	⬆️
...sts/ounit_tests/ounit_analysis_find_files_tests.ml	100.00% <100.00%> (ø)
tests/ounit_tests/ounit_tests_main.ml	100.00% <ø> (ø)
compiler/core/lam_stats_export.ml	91.66% <92.00%> (+0.55%)	⬆️
analysis/src/find_files.ml	82.02% <85.36%> (+4.13%)	⬆️

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