[clang] [analyzer] Splitting TaintPropagation checker into reporting and mode… (PR #98157)

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat commented:

Overall LGTM, I added some minor remarks in inline comments.

Also note that with this change we can finally remove the note
```
The ``alpha.security.taint.TaintPropagation`` checker also needs to be enabled for
this checker to give warnings.
```
from the documentation of `optin.taint.TaintedAlloc` (because the `TaintPropagation` modeling checker is now a _dependency_ of it).

https://github.com/llvm/llvm-project/pull/98157