[flang] remove -f[no-]alias-analysis (#74343)

Now that tbaa tags pass is enabled by default, I would like to remove
these flags. `-fno-alias-analysis` was originally intended to be useful
for debugging, but as it also disables tbaa tag generation in codegen,
it turned out to be too noisy.

@banach-space expressed that these flags felt too non-standard.

The tbaa tags pass can be toggled using `-mllvm
-disable-fir-alias-tags=0`