Avoid unnecessary buildInfo read if host supports caching it (avoids in --build scenario) and some reporting cleanup

[sheetalkamat]

Cherry picked cleanup and fixes from #50293
Basically not picking unnecessary additions to report buildInfo size and read/write times

1. Fixes issue where earlier PR (Report aggregate statistics for solution as well as some solution perf numbers #50267) forgot to clear the aggregate diagnostics in watch mode after reporting
2. When manipulating bundle because the d.ts file didnt change, use cached buildInfo instead of reading it again and parsing if available. (This was discovered as part of Report buildInfo size in extendedDiagnostics #50293 and we already do this when reading old program from buildInfo but not when manipulating bundle)