Improve Crossgen2 map file emitter (#35459)

Improve Crossgen2 map file emitter (#35459)

* Improve Crossgen2 map file emitter

I have rewritten the file name emitter with two main goals in mind:

1) Fix the long-standing problem that map file wasn't showing true
RVA's of the individual symbols / nodes, making it harder to
correlate its information with in-memory R2R PE layout.

2) Add section size and statistics section roughly mimicking what
JanV presented in his recent analytic breakdown of R2R contents.

Thanks

Tomas