Deal as well with sending key if key is outdated in the providers nicknym.

- Resolves: #8819, #8832

mock a renamed method.

There was a test in the Keymanager refresher that was testing the
randomness of the refreshing intervals. It was producing a bunch of
intervals and checking that all of them where different. This test
(rarelly) fails some times, but this is not a sign of bad randomness.

- Resolves: #8813

Check if a new fetched key was signed by a old key with the same address.

Please do not merge before: https://github.com/isislovecruft/python-gnupg/pull/150

- Resolves #8112

- some pep8 problems
- some confusion with old and new code after merging
from old keymanager

disabled some tests that were failing, for some reason the twisted
logger doesn't want to be patched?

besides, I don't think it's a good idea to rely on log information for
tests. what is it really that we were trying to test there?

Port of the original commit:
8f1fe8dd4a54fd2bdda2fc78c339ce9b3d0fc331
by Zara Gebru that introduced updating keys in the background.

This was made in the legacy leapcode/keymanager repo, but was lost in
the merge to the unified bitmask-dev.

Original commit message follows:
--------------------------------

- refresh random key in random time
- add get key by fingerprint
- refactor nicknym methods to own file
- tests

- note this do not include a check for
revoked key, since that need some changes
in gnupg

- Related: #6089

Missing yield from _insert_key_docs, which returns a Deferred, was
causing tests to fail.