Move the fast locking implementation out of the .ad files

Some platforms put the fast locking implementation in the C2_MacroAssembler class, while others have it in the .ad files. I'd like to propose that we unify this a bit and move the code out of the .ad files.

The benefit is consistency between the platforms but also that it is easier to work with the C++ code when it is in plain C++ files and not in the .ad files.

This change affects AArch64 and RISC-V