Symbol Builder: PDB auto import of "<unnamed-*>" symbols can result in mismatches and import failure

[wmessmer-msft]

Repro:

• Open a Win11 KD
• dx @$s = Debugger.Utility.SymbolBuilder.CreateSymbols("nt", new {AutoImportSymbols=true})
• .reload
• !vad

When doing PDB auto-import, we do lookup "by name" for types to see if someone manually created a type before we try to import one of the same "name". Unfortunately, various things assign "<unnamed-tag"> or "<unnamed-*>" to "unnamed" symbols (e.g.: non-named unions/structures/etc...).

These names aren't unique... and when we attempt to look up that "name" and find something, it's the WRONG TYPE.

[wmessmer-msft]

Should be fixed by PR #94