[analyzer] Finish moving alpha.core.SizeofPtr to clang-tidy (#95118)

The checker `alpha.core.SizeofPtr` was a very simple checker that did
not rely on path sensitive analysis and was very similar to the (more
complex and refined) clang-tidy check `bugprone-sizeof-expression`.

As there is no reason to maintain two separate implementations for the
same goal (and clang-tidy is more lightweight and accessible than the
Analyzer) I decided to move this functionality from the Static Analyzer
to clang-tidy.

Recently my commit 546c816a
reimplemented the advantageous parts of `alpha.core.SizeofPtr` within
clang-tidy; now this commit finishes the transfer by deleting
`alpha.core.SizeofPtr`.