[clang] [analyzer] Remove inaccurate legacy handling of bad bitwise shifts (PR #66647)

[via cfe-commits]

DonatNagyE wrote:

Sorry for the inaccessible reports, I forgot to specify that the results should go to the server that we use for open-source reviews.

I'd like to skip the conversion of the testcases that I deleted, because there won't be folks "wondering what happened with these reports": In the majority of situations, the report type already "switched over" to `core.BitwiseShift` when that checker was released.

This PR only affects the "undefined behavior, but works in practice" cases where `core.BitwiseShift` does nothing (in the default non-pedantic mode), so the analyzer was able to reach the "old" logic that produces the `core.UndefinedBinaryOperatorResult` reports (which are eliminated by this PR).

Also, even if I wasted some time on converting those testcases, I'd have to delete them in a later commit, because they're completely redundant with the testsuite of `core.BitwiseShift`.

https://github.com/llvm/llvm-project/pull/66647