Fixed imports for all files *within* `libc/src/string/memory_utils`.
Note: This doesn't include **all** files that need to be fixed.

Fixes #86579

This is a part of #97655.

Reverts llvm/llvm-project#98075

bots are broken

This is a part of #97655.

Codify that we use lower_case for
readability-identifier-naming.ConstexprFunctionCase and then fix the 11
violations (rather than codify UPPER_CASE and have to fix the 170 violations).

GCC reports an instance of -Warray-bounds in block_offset.  Reimplement
block_offset in terms of memcpy_inline which was created to avoid this
diagnostic. See the linked issue for the full trace of diagnostic.

Fixes: https://github.com/llvm/llvm-project/issues/76877

Same as #73939 but also fix `libc/src/string/memory_utils/op_aarch64.h`
that was still using `deferred_static_assert`.

Reverts llvm/llvm-project#73939

This broke libc-aarch64-ubuntu build bot 
https://lab.llvm.org/buildbot/#/builders/138/builds/56186

This is step 4 of
https://discourse.llvm.org/t/rfc-customizable-namespace-to-allow-testing-the-libc-when-the-system-libc-is-also-llvms-libc/73079