Encourage Hypothesis to explore a larger range for NotEnoughTokens

This should reduce the number of spurious changed-coverage reports.

hooray, more than a one-off fix

Use trial multiprocess feature even when collecting coverage

encourage Tahoe-LAFS nodes launched in the test suite to exit eventually

Previously we had it searching [1, inf] to discover the boundary at 2 ** 63.
Now we bias its distribution exponentially and hopefully find the very large
boundary sooner.

Also, remove a data() usage as long as I'm here.

Add automatic retries for some Tahoe-LAFS upload errors

If there are not enough reachable storage servers, try again.  Usually the
client node will manage to connect to some more eventually.

Include linting tools in test requirements.

Add some recovery-related endpoints

this will come in handy for building strategies for testing SQL interactions

Fix bugs in a client resource test which caused spurious fails and successes

Add Tahoe-LAFS `upload` and `download` helpers

Before it just ended up with DeferredResource which proves nothing at all.
Now it requires a sufficiently non-error-y status code to be happy.

Change how success is reported for the replication recovery API

Add a GET variation of the endpoint to poll progress and discover completion.

Also factor out the details since we would otherwise have four instances of
them now.

Maybe it always should be?  But configuring only PYTHONPATH is strictly easier
than configuring PATH and PYTHONPATH so I guess we'll let people do that.

By the time this code runs we know PYTHONPATH must be configured correctly
since we import stuff from allmydata elsewhere.

This helps with debugging failures.
Also the directory deletion implementation is broken on Windows anyway and
sometimes fails with errors like:

```
PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'C:\\Users\\RUNNER~1\\AppData\\Local\\Temp\\tmpc8za73y6\\private\\privatestorageio-zkapauthz-v1.sqlite3'
```