[memory] Check if the process name changed when matching buckets

When matching buckets, verify that the process name did not change
between checks.

As this additional check is done on processes only (not on VMOs, which
are one to two orders of magnitude more numerous), and involves a simple
string comparison, this should have only a small performance impact.

Bug: 42055032
Change-Id: I58f6a423e2e05f317921acf7ca78621a2b8ab280
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1653714
Commit-Queue: Étienne J. Membrives <etiennej@google.com>
Reviewed-by: Guillaume Chelfi <chelfi@google.com>