Rollup merge of #148240 - InvalidPathException:master, r=WaffleLapkin

rustc_codegen: fix musttail returns for cast/indirect ABIs

Fixes rust-lang/rust#148239 rust-lang/rust#144986

Explicit tail calls trigger `bug!` for any callee whose ABI returns via `PassMode::Cast`, and we forgot to to forward the hidden `sret` out-pointer when the ABI requested an indirect return. The former causes ICE, the latter produced malformed IR (wrong codegen) if the return value is large enough to need `sret`.

Updated the musttail helper to accept cast-mode returns, made it so that we pass the return pointer through the tail-call path.

Added two UI tests to demonstrate each case.

This is my first time contributing, please do check if I did it right.

r? theemathas

Author: Zalathar