[clang] [clang][analyzer] Check initialization and argument passing in FixedAddressChecker (PR #110977)

[Balázs Kéri via cfe-commits]

balazske wrote:

I was thinking about using `check::Location` in this checker. The real problem is when the fixed address is used (to store or load), not if it is assigned to a pointer. (Or a fixed address becomes escaped.) Or both cases (with the current checks) can be used, but then multiple warnings may occur for the same case (unless the checker is improved to detect such cases).
The current checker produces relatively many warnings on the tested C projects (like [this](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=vim_v8.2.1920_balazske-fixedaddress_new_b9a919d&is-unique=off&diff-type=New&checker-name=alpha.core.FixedAddr)) and many are (I think) no real problems because just a special value is used in pointers but the pointer is not dereferenced.

https://github.com/llvm/llvm-project/pull/110977