Enables api.detach_state on AArch64 with some initial the sub-tests enabled:
- Enables the cross-platform signal state tests on AArch64.
- Ports the assembly to push and pop all the general-purpose registers, fill them with sentinel values, and test them on a detach from the code cache.
As part of this, adds some general assembly support:
- @P@ expands to # in cpp2asm.
- Adds REG_SP and JUMP_NOT_EQUAL cross-platform asm_defines.
- Adds a missing dep on detach_state_shared.h for the asm code.
Still left to do for future work:
- Check SIMD registers.
- Check flags.
- Check stack.
- Detach from DR rather than the cache.
Issue: #4698