Full support for exception sets in value numbering.

Full support for exception sets in value numbering.

New method that add exception sets:
  fgValueNumberAddExceptionSet
  - fgValueNumberAddExceptionSetForIndirection
  - fgValueNumberAddExceptionSetForDivision
  - fgValueNumberAddExceptionSetForOverflow
  - fgValueNumberAddExceptionSetForCkFinite

Refactoring work added methods:
 VNEvalShouldFold - method to decide if constant folding should be performed
 EvalUsingMathIdentity - Uses math identities to simplify value number exoressions
 Renamed fgValueNumberHelperMethVNFunc to fgValueNumberJitHelperMethodVNFunc

Removed the suffixes from the method headers comments

Commit migrated from https://github.com/dotnet/coreclr/commit/4a6f0c8f0c706c3a5ed5e98feeca80de1da57b5d