linker: keep dotted export names from becoming forwarders

[honkstar1]

Summary

• Match MS link's handling of dotted /EXPORT: names: only export=module.symbol is a forwarder.
• Keep plain dotted symbols like __RTFM.autortfm_is_context_status as normal exports.
• Fixes AutoRTFM/RADLINK DLLs collapsing these exports into one unnamed forwarder, which leaves runtime imports unresolved.

Validation

• Built D:\devel\git\raddebugger\build\radlink.exe with MSVC 14.50 release flags.
• Relinked temp AutoRTFM/CoreUObject DLLs from the Fortnite .rsp files and checked dumpbin /exports:
  • AutoRTFM now exports __RTFM.autortfm_is_context_status.
  • CoreUObject now keeps its __RTFM.?... dotted exports instead of an unnamed forwarder.

[honkstar1]

Closing as implemented upstream by 1091801. The upstream alias/nonempty condition distinguishes an actual forwarder from a plain dotted export name, so the production fix in this PR no longer needs to be carried.

The refreshed #842 retains a declarative regression covering both a plain AutoRTFM dotted export and a real name=module.symbol forwarder. Both pass in the refreshed suite. #892 no longer carries a duplicate dotted-export fix.