[clang] [clang][analyzer] Add "pedantic" mode to StreamChecker. (PR #87322)

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

Good change, I have a few minor suggestions that tweak comment placement.

I felt that it's confusing to have an "Add a transition for" comment directly followed by a seemingly unrelated `if (!PedanticMode)` block -- my suggestions swap the comment and the `if` block, but you could also e.g. prefix the comment with "In pedantic mode, also..." to clarify the logical connection between the `if` and the rest of the comment.

As an unrelated note, please explain this checker option to the documentation of the checker (in addition to the `Checkers.td` change).

https://github.com/llvm/llvm-project/pull/87322