[compiler-rt] [asan] Fix `unknown-crash` being reported for multi-byte errors, and incorrect memory access addresses being reported (PR #144480)

[via llvm-commits]

wxwern wrote:

>From the discussions here so far I believe the following would be most adequate and achieve the same goal:

- `ACCESS_MEMORY_RANGE` reports `__offset` instead of `__bad` to `ErrorGeneric`

- `ErrorGeneric::ErrorGeneric` is updated to use `__asan_region_is_poisoned` for error message classification*, i.e., `shadow_addr = __asan_region_is_poisoned(addr, size)` instead of `shadow_addr = MemToShadow(addr)`
 
\*assuming it's okay to have the caveat mentioned [above](https://github.com/llvm/llvm-project/pull/144480#issuecomment-3130379761)

I'll proceed with restructuring this PR if there're no objections.

https://github.com/llvm/llvm-project/pull/144480