Add runtime MVID checks for composite images

[trylek]

This change introduces runtime consistency checks that make sure that for component assemblies of component images we're loading the same versions of these assemblies (with matching MVID). The change has the following aspects:

1. Producing new R2R header table ManifestAssemblyMvids in Crossgen2;
2. Consuming the new table at runtime and using it to implement the consistency checks;
3. Change to R2RDump to support dumping the new R2R header section;
4. Update of the R2R format spec to include the new table.

I'm still testing the change locally and I intend to author a negative unit test but from my perspective the change should be code complete so I'm looking forward to feedback.

Thanks

Tomas

[davidwrighton]

@mangod9, @dotnet/crossgen-contrib Before we ship, we need to figure out what to do about hammer servicing, as a hammer service event will cause a failfast with this, but otherwise, this looks ok.

[trylek]

Thanks David and Anton for your feedback. Just to set the right expectations, this is supposed to be a mitigation of the large version bubble consistency issue, not its full resolution. In particular, while the proposed update to the R2R format also supports MVID tables for single-input compilations in large version bubble mode, I haven't implemented the consistency checks for this case as they would be more costly and my current understanding is that it's not a shipping scenario.

[mangod9]

We should discuss hammer servicing during our cg2 sync.