Revert "[AArch64][compiler-rt] Add memcpy, memset, memmove, memchr builtins. (#77496)"

This reverts commit 3ab8d2aa.

This change is causing issues running lit tests on many bots including:
- https://lab.llvm.org/buildbot/#/builders/197/builds/12119
- https://lab.llvm.org/buildbot/#/builders/184/builds/9792
- https://lab.llvm.org/buildbot/#/builders/93/builds/18455
- https://lab.llvm.org/buildbot/#/builders/231/builds/19858
- https://lab.llvm.org/buildbot/#/builders/121/builds/38426
- https://lab.llvm.org/buildbot/#/builders/230/builds/23990
- https://lab.llvm.org/buildbot/#/builders/57/builds/32391
- https://lab.llvm.org/buildbot/#/builders/247/builds/13502
- https://lab.llvm.org/buildbot/#/builders/275/builds/3601
- https://lab.llvm.org/buildbot/#/builders/269/builds/4211
- https://lab.llvm.org/buildbot/#/builders/18/builds/14161
- https://lab.llvm.org/buildbot/#/builders/19/builds/23893
- https://lab.llvm.org/buildbot/#/builders/37/builds/30295
- https://lab.llvm.org/buildbot/#/builders/77/builds/33979