Introduce BBJ_EHFAULTRET (#84467)

Introduce BBJ_EHFAULTRET (#84467)

The IL `endfinally` and `endfault` instructions are aliases,
imported in the JIT IR as `BBJ_EHFINALLYRET`.

Introduce `BBJ_EHFAULTRET` for cases within `fault` clauses.

This simplifies some code, and makes it more clear when writing
code that `fault` clauses need to be considered, separately from
`finally` clauses.

To do this, after importing EH clauses, convert any `BBJ_EHFINALLYRET`
as necessary. Also, try/finally cloning, which (sometimes) converts
`finally` clauses to `fault` clauses, needs to update the corresponding
`BBJ_EHFINALLYRET`. When creating new try/fault clauses for synchronized
functions, use `BBJ_EHFAULTRET` now.

Fixes #84307