Move hal-posix-io and hal-win-io into mruby-io/ports/posix/ and
mruby-io/ports/win/. Platform sources are now compiled
automatically based on conf.ports setting. Remove HAL
auto-detection logic from mrbgem.rake.
Co-authored-by: Claude <noreply@anthropic.com>
Yukihiro "Matz" Matsumoto