The test was flaky because it assumed that AllocatedAssemblerBuffer
would eventually return an address within near-call range. Rarely, this
did not happen (within the retry limit), and so the test would crash.

This fix allocates a single, kMaxWasmCodeMemory-sized buffer for the
test, and generates call sequences within that buffer.

BUG=v8:8245

Change-Id: I4b44d897c6cbda15a18ab992fa57805de3b2db29
Reviewed-on: https://chromium-review.googlesource.com/c/1347484Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Jacob Bramley <jacob.bramley@arm.com>
Cr-Commit-Position: refs/heads/master@{#57898}