[lldb] Scope XML register type IDs to features (#216384)
This change separates XML register-type lookup from ownership:
- Uses a temporary type registry for each `<feature>`, allowing IDs to
be reused safely across features.
- Keeps all parsed types alive in process-owned storage.
- Uses one common registry for enums, flags, and future vector/union
types.
- Prevents stale enum pointers and cross-feature type reuse.
Relates to #214444.
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Co-authored-by: Bar Soloveychik <barsolo@fb.com>
