Related to T2367

- blackify all the python files,
- enable black in pre-commit,
- add a black tox environment.

This aligns with other journal clients. This lets the main loop being done by
the journal client base class.

Origin model no longer allows types.

Related to f533f62bbf114cfcc29f7c72307c4dfbe99cf048

The option was renamed in swh-journal v0.0.27

Related to D2820

Old task have a parse_ids passed in their kwargs arguments, which pass through
the index_list. This is no longer used but currently break.

This commit fixes the behavior to allow the task to continue its work.

Related https://sentry.softwareheritage.org/share/issue/5ccef623905747b7b4cff7de859aaceb/

Prior to this commit, this used the storage ones.

The decorator @process_metrics is already doing this job. The send_metric
function is for the other endpoints which do not return a summary.

Related https://sentry.softwareheritage.org/share/issue/518b76d7d7d244f8b88d1757599035b2/

Prior to this commit, this ended up running twice the insertion query. First
time, on conflict actually inserting data, then running again. The second extra
time being a noop (plus costing extra time), thus returning a summary of no new
elements inserted.

The tests must be improved to actually check the insertion output. It's not the
case or it would have been caught already.

This happens when we find two metadata files each with at least two authors.

The codemeta module was missing 'merge_values' even though it was the logical place,
and its tests were scattered around multiple other modules' tests.

This commit moves all these in codemeta.py and test_codemeta.py.

This also tries to type a tad better the indexers.

This will allow to send metrics at some point.

This allowed to chain indexers together.
It's not used, so to simplify maintenance, remove it.

This also clarifies the intent.

Similarly to what we do in the swh.storage.

Related to D2580

`storage.origin_get` can return None as origin. This adds the behavior to skip
those None origin instead of failing the indexing task.

Related https://sentry.softwareheritage.org/share/issue/8551b4a0ed694e09ad1ad7bde047e48f/

This should improve the textual content reading queries.

Related to T1788

In production, the previous query version takes too long to finish. This ended
up with timeouts (with query still running in the pg backend). Accumulating
similar new queries.

Counter-intuitively, specifying twice the range query to use (both in
content_mimetype and content_fossology_license), the execution now returns
immediately.

Close T1788

And re-raise them through the RPC layer.

This is now required by swh-core, as exceptions are no longer pickled.

Required by swh-storage >= v0.0.172.