... between the interpreter and generated code.

Prior to this CL, pre- and post conditions on the output register
array differed between the interpreter and generated code.

Interpreter
Pre: `output` fits captures and temporary registers.
Post: None.

Generated code
Pre:  `output` fits capture registers.
Post: `output` is modified if and only if the match succeeded.

This CL changes the interpreter to match generated code pre- and
post conditions by allocating space for temporary registers inside
the interpreter.

Drive-by: Add MaxRegisterCount, RegistersForCaptureCount helpers.

Bug: chromium:1067270
Change-Id: I2900ef2f31207d817ec7ead3e0e2215b23b398f0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2135642
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67268}