Each assembler has it's own way to place breakpoints:

  - stop() for arm, mips*, ppc* and s390.
  - debug() for arm64.
  - int3() for ia32 and x64.

We can mandate a macro-assembler `DebugBreak()` method that all should
implement so one can place a breakpoint in a portable way using a
macro-assembler. This way also assemblers are in line with TurboFan, CSA, Torque
and Liftoff which all have a DebugBreak() facility.

Change-Id: Ic4332bd19ca4db53e01441d54af6632c2c1189f1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2020954Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Pierre Langlois <pierre.langlois@arm.com>
Cr-Commit-Position: refs/heads/master@{#66198}