Thanks, Hypothesis.

Probably useful for implementation later.
Useful for test suite right now.

Helpful for the tests

eg: nix-build --arg trialArgs '["-x"]'

using the wrong words to describe everything.

Fixes for problems arising in integration testing.

Remove unnecessary overrides

not sure this fixes anything but it might fix the PrivateStorageio build which
finds autobahn 19.1.1 instead of autobahn 19.8.1.

I think it is abstractly "more correct" too, maybe, if you can convince
yourself there is such a thing.

So we don't have to override them to get a new version anymore.  Also,
upstream has done a better job of integrating them into the overall system
than we have (with respect to other upstream changes).

Servers require and clients supply passes correctly for renew_lease.

Check the number of passes in add_lease.

This helps the client a lot with lease operations

The native st_size-based approach to size estimation is broken because mutable
and immutable layouts have a different amount of overhead.  So start peeking
inside the share files.

Also, new_length must be respected now because when it is used the part of the
share file we peek at changes.  Also, new_length can *only* truncate so stop
treating it as if it can extend.