Fix X86 disassembly and a bug regarding ExportedTypes in R2RDump (dotnet/coreclr...

Fix X86 disassembly and a bug regarding ExportedTypes in R2RDump (dotnet/coreclr#20230)

1) X86 CoreDisTools disassembler has a bug in decoding absolute
indirections, interpreting them as RIP-relative offsets. I have
reused the logic that's already in place for patching X64
RIP-relative addresses to take care of this additional case.

2) the CoreDisTools disassembly apparently only produces newline
(0A) characters that don't work well in Notepad and other viewers;
I have forcibly replaced them with the platform newline separator.

3) I hit a bug in available type decoding - the logic wasn't
properly checking whether the type is exported or not.

Thanks

Tomas

Commit migrated from https://github.com/dotnet/coreclr/commit/31955025defa95915c0532773dbf5cb4a932953a