Fix FOSS specs running under EE

There were a few problems here:

1. The implementation imports some components from `ee_else_ce`, while
   the FOSS spec was importing all from FOSS. This meant that the spec
   was asserting against the wrong component.
2. The EE components have injections without default values. Under Vue
   3, this results in a warning being logged, which fails the test. The
   tests now provide sensible values for those injections.
3. It seems that calling `wrapper.props()` on a Vue wrapper wrapping a
   component that extends another component doesn't work as expected
   under Vue 3. The props object is empty, as if the component doesn't
   define any props. This is either a bug in `@vue/test-utils@2`, or a
   bug in our compat layer `vue-test-utils-compat`. The workaround for
   now is to explicitly redeclare the props on the component that
   extends the other.