[clang] [analyzer][NFC] Rename class `StackFrameContext` to `StackFrame` (PR #195802)

[Donát Nagy via cfe-commits]

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

LGTM; the changes are completely mechanical and I trust @tigbr that he didn't miss any occurrence of the string 'StackFrameContext' 😄 

I'm a bit surprised to see that this touches almost 500 lines (I would have guessed ~200) but the checkers are less affected and everything is very mechanical, so I think this is OK overall.

@steakhal WDYT? Is there any obstacle to merging this?

https://github.com/llvm/llvm-project/pull/195802