[sanitizer][msan] The LLVM part of the LoongArch memory sanitizer implementation

This patch enabled msan in LLVM and fixed all failing tests in
check-msan.

It does not add VarArgHelper implementation on LoongArch, which
will be done separately later. And it adds a test for VarArgNoOpHelper,
which is based on the X86 one.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D152692