Pgo phase2 (#47055)

Pgo phase2 (#47055)

Funnel PGO instrumentation data from runtime to crossgen2

- Representation of instrumentation data within crossgen2 and dotnet-pgo
- New uncompressed mibc format for easier debugging/faster processing
- Storage of instrumentation data in mibc file
- Parser for instrumentation data to load from mibc file
- Translation of crossgen2 in memory representation of instrumentation data from managed form to jit

Future PGO work will include
- Instrumentation data storage and extraction from R2R files
- Move Pgo type handle histogram processing into JIT (which will make type guessing work in crossgen2 as well as in the runtime)
- Triggers for controlling Pgo data extraction
- Size control for pgo instrumentation data