[cleanup][test] Don't rely on __COUNTER__ in expectations

Several of the cctest/test-bytecode-generator/* tests used to rely
on the __COUNTER__ C++ compiler macro, which could cause spurious
test failures due to mismatched expectations when usages of that
macro were added or removed elsewhere in the code. This patch switches
to a custom, controllable static counter variable instead, to make
the tests' behaviors self-contained.

Bug: v8:12244
Change-Id: I4d875b6095e4ee4ef91933ab8c60c89054d1894a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3186836Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77111}