codegen: emit lookupFunction dispatch for external jump-table targets

[jlsandri]

Problem

When a [[jump_tables.table]] entry in the TOML config has targets that live outside the enclosing function's boundary, the previous codegen silently filtered them out. Those external targets would then be unreachable from the recompiled jump, which at runtime manifests as a wrong branch destination (or a no-op, depending on the dispatch path).

Fix

• Teach analysis to distinguish internal jump-table targets (which still use goto-to-label dispatch inside the function body) from external ones.
• Emit a runtime lookupFunction(0x…) dispatch call for the external targets, matching the fallback path already used for unresolved static J/JAL sites (per the README's "unresolved static J/JAL" behaviour).
• Add an externalJumpTableTargets field to AnalysisResult so the two categories can be separated during codegen instead of being decided in the emitter.

Scope

• ps2xRecomp/include/ps2recomp/code_generator.h: +4 / -0
• ps2xRecomp/src/lib/code_generator.cpp: +46 / -9

Rationale

The recompiler already has a principled fallback for unresolved static calls (runtime->lookupFunction(...)), so routing external jump-table targets through the same mechanism fits the existing model and makes the previously-filtered targets actually reachable at runtime.

[jlsandri]

Closing as part of a batch cleanup after #107 landed. The runtime ecosystem refactor in #107 substantially reworked the files this PR touched, and I would like to re-audit the underlying fix against the new code structure before putting it back in front of you. If the fix is still needed after that re-audit, I will re-open as a focused PR rebased onto current main. Thanks for your patience.