[clang] [clang][analyzer] Support 'getdelim' and 'getline' in StreamChecker (PR #78693)

[via cfe-commits]

https://github.com/NagyDonat approved this pull request.

Looks reasonable.

My only concern is that several recent changes introduced similar, but separate `evalXXX` methods that are used for modeling just one or two standard functions. I have a vague suspicion that these could be "standardized" (e.g. by moving their common parts into helper functions) to reduce the length and complexity of the code.

https://github.com/llvm/llvm-project/pull/78693