feat: cache binaries for released versions accros workflow runs

[manjunathSurendrakumar]

Code Changes:

src/download.ts:

✅ Added cacheFile and find imports
✅ Modified downloadPiperBinary() to check cache first
✅ Added caching after download
✅ Maintained backward compatibility

src/github.ts:

✅ Added cacheFile and find imports
✅ Modified buildPiperFromSource() to check cache first
✅ Added caching after build
✅ Removed TODO comments
✅ Added cleanup of temp directories

src/build.ts:

✅ Added cacheFile and find imports
✅ Modified buildPiperInnerSource() to check cache first
✅ Added caching after build
✅ Added cleanup of temp directories

Test Files Updated:
✅ test/github.test.ts
✅ Updated 4 existing tests to mock toolCache.find()