Use MockLogAppender.capturing

[rjernst]

Many uses of MockLogAppender predate the addition of the helper method to create a Releasable for restoring logging, which allows the use of try-with-resource blocks. This commit converts current existing uses of MockLogAppender to use capturing.

relates #106425

[elasticsearchmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)

[rjernst]

Note that there are further cleanups here possible. For example, the creation of the MockLogAppender could happen as part of capturing, and the returned object could be the appender itself. However, for this PR I chose to make as mechanical a change as possible as a first step.

[ldematte]

LGTM, only one minor nit: do we still need to call explicitly mockAppender.assertAllExpectationsMatched();? Since an identical check is done by the Releasable, maybe it's redundant and we can clean up them (can be as part of a follow-up, as you noted further cleanups are possible).

[rjernst]

do we still need to call explicitly mockAppender.assertAllExpectationsMatched();

The check is not identical. It's actually checking that assert was called. Without the explicit assert call, a test will fail. Basically the releasable checks that an assert was done, but it doesn't presume that assertion should happen when releasing (though maybe it should, we can discuss for a followup).