#8987 fix versioning in debian package (and other things)

I took the opportunity to fix a bunch of server-side issues:

• report version correctly in code installed by the debian package. Now there's a /usr/bin/soledad-server command that can do --version.
• make server restart after an upgrade.
• a bit of refactor in entrypoints to wait for checks before starting up services.

Closes #8987 (closed)