installing sqlite3, but only when needed

[nimonian]

I once removed sudo apt install sqlite3 as it was running with each test and slowing things down horribly.

Github's (giant) test runner image has it anyway.

But we're running into scenarios where we want to assert the presence of sqlite3 (e.g. local development with act.

Great news is that the new approach to testing with ./test.sh 1a will just install sqlite3 once, and only if needed.

So we get the best of all worlds.

[nimonian]

On second thought, this could break local testing on systems that don't have apt

A solution that only checks/installs sqlite3 when running as an action would be better