[llvm] [CGP] Consider arguments and ret values in `dupRetToEnableTailCallOpts` (PR #76613)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

Updated this to explicitly looking for candidate intrinsics / `strcpy`, as I don't think only looking for first argument was robust enough to avoid phi folding to ret in all cases (now evaluating it on the compile-time tracker for regressions).

https://github.com/llvm/llvm-project/pull/76613