[WebAssembly] Do not use EHCatchret symbols with wasm EH

D94835 added support for WinEH to export public symbols pointing to
basic blocks which are catchret targets for use with Windows CET.
Wasm currently doesn't support public symbols to non-function code
addresses (they get treated like new functions in asm but then don't
lower to object files correctly).
It created them unconditionally for all catchret targets.

This change disables those symbols unless the exceptionHandlingType
is WinEH (since they aren't used with ExceptionHandling::Wasm)

Differential Revision: https://reviews.llvm.org/D96824