Auto merge of #113430 - Zalathar:hash, r=b-naber

Remove `LLVMRustCoverageHashCString`

Coverage has two FFI functions for computing the hash of a byte string. One takes a ptr/len pair (`LLVMRustCoverageHashByteArray`), and the other takes a NUL-terminated C string (`LLVMRustCoverageHashCString`).

But on closer inspection, the C string version is unnecessary. The calling-side code converts a Rust `&str` into a `CString`, and the C++ code then immediately turns it back into a ptr/len string before actually hashing it. So we can just call the ptr/len version directly instead.

---

This PR also fixes a bug in the C++ declaration of `LLVMRustCoverageHashByteArray`. It should be `size_t`, since that's what is declared and passed on the Rust side, and it's what `StrRef`'s constructor expects to receive on the callee side.

compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs

@@ -373,12 +373,7 @@ pub(crate) fn write_mapping_to_buffer(
     }
 }
 
-pub(crate) fn hash_str(strval: &str) -> u64 {
-    let strval = CString::new(strval).expect("null error converting hashable str to C string");
-    unsafe { llvm::LLVMRustCoverageHashCString(strval.as_ptr()) }
-}
-
-pub(crate) fn hash_bytes(bytes: Vec<u8>) -> u64 {
+pub(crate) fn hash_bytes(bytes: &[u8]) -> u64 {
     unsafe { llvm::LLVMRustCoverageHashByteArray(bytes.as_ptr().cast(), bytes.len()) }
 }