Rollup merge of #91675 - ivanloz:memtagsan, r=nagisa

Add MemTagSanitizer Support

Add support for the LLVM [MemTagSanitizer](https://llvm.org/docs/MemTagSanitizer.html).

On hardware which supports it (see caveats below), the MemTagSanitizer can catch bugs similar to AddressSanitizer and HardwareAddressSanitizer, but with lower overhead.

On a tag mismatch, a SIGSEGV is signaled with code SEGV_MTESERR / SEGV_MTEAERR.

# Usage

`-Zsanitizer=memtag -C target-feature="+mte"`

# Comments/Caveats

* MemTagSanitizer is only supported on AArch64 targets with hardware support
* Requires `-C target-feature="+mte"`
* LLVM MemTagSanitizer currently only performs stack tagging.

# TODO

* Tests
* Example

compiler/rustc_span/src/symbol.rs

@@ -876,6 +876,7 @@ symbols! {
         mem_zeroed,
         member_constraints,
         memory,
+        memtag,
         message,
         meta,
         metadata_type,