PPC: [codegen][cleanup] Unify assembler's support for DebugBreak().

Port 86d4b9f6

Original Commit Message:

    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.

R=pierre.langlois@arm.com, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: If2fb5ed99b4477142579e29fc5288d0768fd48c7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2047463Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#66207}

src/codegen/ppc/macro-assembler-ppc.h

@@ -764,7 +764,6 @@ class V8_EXPORT_PRIVATE MacroAssembler : public TurboAssembler {
   void InvokeFunction(Register function, Register expected_parameter_count,
                       Register actual_parameter_count, InvokeFlag flag);
 
-  void DebugBreak();
   // Frame restart support
   void MaybeDropFrames();