Moves the temporary register allocator out of the bytecode array
builder into TemporaryRegisterAllocator class and adds unittests.
Particular must be taken around the translation window boundary
motivating the addition of tests.
Also adds a Clear() method to IdentityMap() which is called by
the destructor. This allows classes to hold an IdentityMap if
they are zone allocated. Classes must call Clear() before the zone
is re-cycled or face v8 heap corruption.
BUG=v8:4280,v8:4675
LOG=N
Review URL: https://codereview.chromium.org/1651133002
Cr-Commit-Position: refs/heads/master@{#33686}
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