This change adds new flavors of Visit() methods for obtaining
expression results:

- VisitForAccumulatorValue() which places result in the accumulator.
- VisitForRegisterValue() which places the result in a register.
- VisitForEffect() which evaluates the expression and discards the result.

The targets of these calls place the expression result with
result_scope()->SetResultInRegister() or
result_scope()->SetResultInAccumulator().

By being smarter about result locations, there's less temporary
register usage. However, we now have a hazard with assignments
in binary expressions that didn't exist before. This change detects and
DCHECK's when a hazard is detected. A follow on CL will address this.

There are consequential changes to test-bytecode-generator.cc and
this change also adds new bytecode macros A(x, n) and THIS(n) for
register file entries for arguments and this.

BUG=v8:4280
LOG=NO

Review URL: https://codereview.chromium.org/1392933002

Cr-Commit-Position: refs/heads/master@{#31445}