Previously, we would both instrument the code, and add/remove
BreakPointInfo objects through BreakLocation. This is bad design and
unsuitable for having two different code kinds.

We would now add/remove BreakPointInfo objects, and use that as source
of truth when instrumenting the code. If we have both bytecode and FCG
code, we would simply apply these break points twice to either.

Notable changes:
- Removed many functionality from BreakLocation.
- Instrumentation (patching code for breaks) happens by applying break
  point info onto code.
- Instrumentation (code patching) is done by the BreakIterator. For
  bytecode, it's BytecodeArrayBreakIterator. For FCG code, it's
  CodeBreakIterator.
- Changes to code instrumentation mostly involves clearing current
  instrumentation and then (re-)applying break points.
- DebugInfo can now reference both bytecode and FCG code.

R=jgruber@chromium.org, mstarzinger@chromium.org
BUG=v8:5265

Review-Url: https://codereview.chromium.org/2238893002
Cr-Commit-Position: refs/heads/master@{#38596}