Closes T2803.

Before, ls history/by-date/ took a few seconds and it was getting slower
the more metadata were stored in the sqlite cache. This was because it
would query the metadata cache for all SWHIDs in history.

Now, a new column has been created to store a relation (rev swhid, date)
meaning we only need to do one query to get all history with a specific
date prefix.

Closes T2802.

Closes T2784.

Closes T2676

Closes T2785

most notably drop "virtual" from filesystem everywhere for consistency

- Remove manual direntry cache manipulation
- Remove unnecessary by-hash/ sharding depth attribute
- Time optimization for by-date/ partial results
- More extensive unit testing for by-date/

Closes T2795.

Closes T2773.

Do not unnecessarily format string (eg: when log statement is below
current log level).

Closes T2772.

During development of new features, enabling the DEBUG log-level every
time to hunt down a runtime exception is unpractical since the DEBUG
level is very verbose and does not include the exception traceback.
Using the logging.exception() method fixes all these issues.

The asizeof() introduced a very heavy overhead which made swhfs unusable
when relying on many asizeof calls (eg: storing history exploration in
the direntry cache with a history containing >1000 commits).

The heuristic to calculate the size of a FuseEntry is based on
experimental results from repositories with various history sizes (10K,
100k, ...)

Pre-fill the direntry cache with all the sub-entries once the history
has been retrieved.

Closes T2695.

The readdir() endpoint is now O(N) instead of O(N²) since we do not go
through all entries every time, but only those after the readdir()
offset.

Closes T2723.

Rework existing mock archive to account for a new graph backend.

Closes T2659.

Rationale: ease batch commit workloads.

Closes T2725.

rationale:
- it is consistent with SwhFS which we are now using in doc
- FUSE is an implementation detail, which has no place in user-facing names
- it is consistent with other FUSE-based FS (sshfs, RepoFS, etc.)

Closes T2708.

Closes T2716.

Closes T2711.

Closes T2709.