Update to upstream version '2.0.0'
with Debian dir 2052ddda8de37d199917892c928cf05253eac71c

Update to upstream version '1.0.2'
with Debian dir c1afa848646e12461a43fbcdaa1d6c299ea7375d

Update to upstream version '1.0.1'
with Debian dir 999fb1134aecb2cebd49e45b07d5aae55f3817fd

Update to upstream version '1.0.0'
with Debian dir 617457eebf033bf3c5fd4687c783c023155302df

Related to T4102

Related to T4102

Update to upstream version '0.5.2'
with Debian dir cc1cd301e95e912bb6bdff02e6a42e0849c21f20

Update to upstream version '0.5.1'
with Debian dir cd0f262be1819457baa92becea350caa986b2b29

This runs only the naive_client tests and not the remote.

Update to upstream version '0.5.0'
with Debian dir 4f9829c82724421fb7054e5b7be7b82ab5a1d29f

Related to T3518

which weight ~40Mib

The swh.graph.client and swh.graph.naive_client must be packaged separately to allow the
vault to use the optional graph dependency. We need the tests to run in the packaging
though. The current conftest.py mixes both server and client code though. Delaying
imports this way will allow the packaging to run accordingly [1].

[1]
```
pytest -k "not remote" swh/
```

Related to T3518

This is a 40 to 70% speed-up of the overall run time (wall clock).

Most of the time is spent maxing out the CPU in the Python process.
This change has two effects:

1. lines are joined before being encoded (instead of encoding them one-by-one)
2. larger network packets are sent, instead of a single packet per line

I don't know which affects the performance, but overall, this is
a consistent 25 to 35% speed-up to the overall run time of
SimpleTraversalView.

This required a minor Backend refactoring to make it work
without context managers.

this is equivalant to git2graph, but does not rely on the git object
storage (and of course does not crawl revisions)