[clang] [clang][StaticAnalyzer] Adding getentropy to CStringChecker. (PR #83675)

[Balázs Kéri via cfe-commits]

balazske wrote:

Currently it looks OK to add `getentropy` to this checker because it is a string related function in a way. Otherwise it looks like that many of the checks (for buffer access, and buffer invalidations) that are implemented in `CStringChecker` could be moved to `StdLibraryFunctionsChecker` (but this can be more work). 

https://github.com/llvm/llvm-project/pull/83675