scripts: unit-test: Constrain test setups to current project

self.package now reflects the top-level meson project name. Using this,
prevent incorrect propagation of configuration into subprojects using
the usual meson scope syntax.

Further, now that we're using the scope syntax, meson outputs a
different error message:

```
$ meson test --setup=stdplus:__likely_not_a_setup__ -C build __likely_not_a_test__
Unknown test setup 'stdplus:__likely_not_a_setup__'.
```

Adjust the regex that performs the setup error test.

Change-Id: Ia15c0406323f025fff318cb1c1e4a92605d19c96
Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
1 file changed