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

Previously, bitwise shifts with constant operands were validated by the
checker `core.UndefinedBinaryOperatorResult`. However, this logic was
unreliable, and commit 25b9696b added
the dedicated checker `core.BitwiseShift` which validated the
preconditions of all bitwise shifts with a more accurate logic (that
uses the real types from the AST instead of the unreliable type
information encoded in `APSInt` objects).

This commit disables the inaccurate logic that could mark bitwise shifts
as 'undefined' and removes the redundant shift-related warning messages
from core.UndefinedBinaryOperatorResult. The tests that were validating
this logic are also deleted by this commit; but I verified that those
testcases trigger the expected bug reports from `core.BitwiseShift`. (I
didn't convert them to tests of `core.BitwiseShift`, because that
checker already has its own extensive test suite with many analogous
testcases.)

I hope that there will be a time when the constant folding will be
reliable, but until then we need hacky solutions like this improve the
quality of results.