[compiler] Support optional/logical/etc within try/catch (#35606)

Adds support for value terminals (optional/logical/ternary/sequence)
within try/catch clauses.

Try/catch expressions insert maybe-throw terminals after each
instruction, but BuildReactiveFunction's value block extraction was not
expecting these terminals. The fix is to roughly treat maybe-throw
similarly to goto, falling through to the continuation block, but there
are a few edge cases to handle.

I've also added extensive tests, including testing that errors correctly
flow to the catch handler.