Fix field offset computation for large version bubble (#25029)

Fix field offset computation for large version bubble (#25029)

There was a discrepancy in field offset calculations at crossgen time
and at runtime in some rare cases due to the alignment of a derived
class offset.
The issue happened due to MethodTableBuilder::NeedsAlignedBaseOffset not
taking into account the fact that the module of the parent and child
class can both be in large version bubble.

We also had a bug in the PEDecoder::GetNativeManifestMetadata. When it
was called for regular crossgened image without large version bubble, it
left the pDir uninitialized due to the fact that there was no
READYTORUN_SECTION_MANIFEST_METADATA. And then it tried to dereference
that.