This ensure we don't have any remaining `generic_type_validator` call
that have not been optimized away.

This indirection seems useless and is probably the remains of some long
forgotten rituals.

This should reduces function calls and speeds things up.

It might be useful to introduce even more specialized validator in the
future. It would also be useful to skip the intermediate try/except.

Some of this will be done in later changesets.

This is currently doing nothing, but prepare for actually changing the
generic validator into faster specialized variants.

Before this change we would do the following :

1) translate from_disk's object into `dict`,
2) sort these dict,
3) feed the list to `Directory.from_dict`,
4) create DirectoryEntry from these dict.

Skipping the directory creating and directly creating the
DirectoryEntries provide us with a small but stable and noticeable
performance win.

We tested this change on simple information of the Mercurial loader,
with a noop-loader stockage:

    swh loader run mercurial https://foss.heptapod.net/mercurial/mercurial-devel directory=/data/repos/mercurial-devel

= Median time of 3 run =
before: 11 minute  56 seconds
aftere: 11 minute  50 seconds

On a profile of the same run, the `to_model` call of the from_disk's `Directory` class took the following percentage:
before: 17%
after:  15%

Do not create model object while sorting entry before creating model
object.

This is another case of "let us create object X to prepare the creation
of object X", slowing things down.

In practice, we will likely skip this code-path after the next
changeset, however this seems useful to get this performance footgun
out the way.

We tested this change on simple information of the Mercurial loader,
with a noop-loader stockage:

    swh loader run mercurial https://foss.heptapod.net/mercurial/mercurial-devel directory=/data/repos/mercurial-devel

= Median time of 3 run =
before  12 minutes 59 seconds
after:  11 minute  56 seconds

On a profile of the same run, the `to_model` call of the from_disk's `Directory` class took the following percentage:
before: 24%
after:  17%

Before this change, a Directory object was built to compute the `id` of
we fed to the Directory object we built for `to_model`.

We tested this change on simple information of the Mercurial loader,
with a noop-loader stockage:

    swh loader run mercurial https://foss.heptapod.net/mercurial/mercurial-devel directory=/data/repos/mercurial-devel

= Median time of 3 run =
before: 17 minutes 48 seconds
after:  12 minutes 59 seconds

On a profile of the same run, the `to_model` call of the from_disk's `Directory` class took the following percentage:
before: 43%
after:  24%

Format was changed in 752fb81d.

This is needed by swh-scrubber when recomputing the hash of such snapshots.

It allows building a snapshot manifest despite some branches being
unresolved (instead of raising an error).

This feature was removed in 57ae405d
but in the end, Snapshot.compute_hash() will need to use it so that
swh-scrubber does not crash when checksum such snapshots.

hypothesis.strategies.integers() is inclusive, but microseconds values
greater or equal to 1 million are rejected by the model

This allows callers to pass different (typically, stricter) strategies
to hypothesis instead of filtering the output; which makes example
generation faster.

It will be used by swh.storage.backfiller (so indirectly, swh.scrubber)
to load directories from the postgresql database, whose schema accidentally
allowed directories with duplicate entries -- without corrupting the
shape of the directory too much.

We can use `format_git_object_from_parts` inside it.

This would be useful for the IPFS bridge, and seems good to complete the
API in any sense.

it's a piece of information used several times in the swh stack.

Related to T3922

Hypothesis: This makes the documentation build fail.

This changes the deprecated :show-nested: instruction to the :nested: one [1].
This also fixes warning about misdefined block [2]

[1] https://sphinx-click.readthedocs.io/en/latest/usage/#directive-click

[2]
```
10:38:38  Warning, treated as error:
10:38:38  /var/lib/jenkins/workspace/DMOD/tests-on-diff/docs/cli.rst:14:Literal block expected; none found.
10:38:38  make: *** [../../swh-docs/Makefile.sphinx:32: sphinx/html] Error 2
10:38:38  make: Leaving directory '/var/lib/jenkins/workspace/DMOD/tests-on-diff/docs'
10:38:38  ERROR: InvocationError for command '/usr/bin/make -I ../.tox/sphinx/src/swh-docs/swh/ -C docs' (exited with code 2)
```

committer=None happens on some malformed commits generated by old dgit
versions ; and it is possible for author=None to happen for the same reason.

these fields are computed attributes and may be removed from the backend
storage. Helps writing tests.

This will be used by swh.storage.backfill's tests.

This reverts commit a0f54362.

This means this commit removes the 'offset' and 'negative_utc'
arguments.

It also removes the 'negative_utc' attribute (which is not used
anymore), but keeps an 'offset' property, which is an alias to
'offset_minutes()'. This is only to keep this commit readable;
the next commit will remove this alias.

This should slightly reduce the memory used by dir/rev/rel objects

A future commit will remove the 'offset' attribute, and rename
'offset_bytes' to 'offset'.

Modules using the `.offset` attribute will need to switch to this new
method to keep working.

This allows keeping compatibility with existing users of the TimestampWithTimezone constructor

'offset' becomes a property instead of an attribute and constructor argument.

This also removes both from the output of `.to_dict()`.

This is step 6 of https://forge.softwareheritage.org/T3752

This will break packages that still use the constructor directly,
ie. swh-storage and swh-loader-git (and tests of swh-loader-core
and swh-loader-svn)

This is needed when recomputing the manifest of git objects with weird offsets.