[clang] [ASAN] Adjust asan instrumented GlobalVariable size to not include redzone (PR #66666)

[via cfe-commits]

b-sumner wrote:

@hctim *any* implementation will have a problem when copying the redzone padding.  That is simply because the redzone is poisoned (hence the name).  Any access to a poisoned location will be reported and the application terminated.  That is how ASAN works.

https://github.com/llvm/llvm-project/pull/66666