Fix AOT try/catch for empty user classes (#2157)

[PurHur]

Summary

• Fix TryCatchHelper::collectCatchOps() to skip TYPE_JUMP opcodes between TYPE_TRY and TYPE_CATCH so nested CFG (e.g. 007-ThrowsWeb) registers catch arms instead of falling through to abort().
• Pre-compile merge bodies before dispatch, split merge entry vs body basic blocks, and lower catch blocks via compileIncludedAtEntry() at the match BB so catch bodies (echo/assign) are reachable in native AOT.
• Reuse existing JIT class ids in declareClass() and add throws_user_class AOT fixture plus TryCatchCollectOpsTest.

Test plan

• vendor/bin/phpunit --filter throws_user_class
• THROWSWEB_AOT_SMOKE_GATE=1 vendor/bin/phpunit test/unit/ThrowsWebAotExecuteTest.php
• Manual: ./phpc build --project examples/007-ThrowsWeb + POST email=bad prints invalid
• Note: in-process bin/jit.php try/catch execute still segfaults on master and this branch (AOT/native path is green).

Closes #2157

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