tests,ci: Move "test-basic" (bare mode) to installed test

tests,ci: Move "test-basic" (bare mode) to installed test

Our CI uses default Docker, which has SELinux labeling but is rather
evil in returning `EOPNOTSUPP` to any attempts to set `security.selinux`,
even if to the same value.

The previous fire 🔥 for this was: https://github.com/ostreedev/ostree/pull/759

The `bare` repo mode really only makes sense as uid 0, so our installed
test framework is a good match for this.  However, the unit tests *do*
work in a privileged container even as non-root, and *also* should
work on SELinux-disabled systems.  So let's teach the test framework
how to skip in those situations.

I tested this both in a priv container (my default builder) and an unpriv
container (like our CI).

At the same time, start executing the `test-basic.sh` from an installed test,
so we get better coverage than before.

This is just the start - all of the sysroot tests really need the
same treatment.

Closes: #1217
Approved by: jlebon