[clang] [analyzer][NFC] Merge the `LocationContext` class into the `StackFrame` class (PR #198211)

[Balázs Benics via cfe-commits]

steakhal wrote:

>> I'd suggest squashing what we currently have.

I can see 39 commits on this PR. We have a rough agreement that the scope of these commits (or the scope of the PR) is fine. So I'd propose an interactive rebase and squash these 39 commits into a single commit with an updated commit message - or you could just keep the squash messages - that might be even better for history.

I don't know what upcoming changes you suggested because I didn't look. We could include them still in this PR, but it depends on their content. This is why I suggested to keep them separate from the squashed content.

After this we would have 2 options:
 - We just merge (in other words) close this PR with the squashed commit only.
 - Or we include the additional commits and squash-merge those as well.
 
 Personally, I'd prefer the easiest: the first option and reserve the suggestions for a subsequent PR - but again, this is just a hunch because I haven't looked what you proposed or how those commits would relate to what I could see here right now.
 
 
 > In my current somewhat tired and pessimistic state of mind I also toyed with the idea of renaming StackFrame (again) and keeping the very widespread class name LocationContext unchanged – in that case this ±2500 line commit could be replaced by a ± few hundred commit (merging the implementations of the two classes + touching the lines that were touched when StackFrameContext was renamed to StackFrame + touching getStackFrame-like methods).
>
> I think the more ambitious plan implemented in this PR is better overall, but I think it is worth to mention this alternative explicitly.
 
 I think @tigbr already put so much effort into this, I want to just get over with this one. This is the direction we want to go. It is just a matter of chunking. I'll try to spare some time and have a thorough look in the upcoming days.

https://github.com/llvm/llvm-project/pull/198211