Remove unused frontend tests

[oliverguenther]

The frontend *.spec.ts were never executed since switching the CI to turbo-tests. They were not really kept up-to-date before either. To avoid confusion, let's remove them altogether. Components can be tested in the primer repo, or using system test

[myabc]

@oliverguenther I realise that we're not running these specs on CI currently - and that the testing strategy going forward is Capy+Cuprite feature specs, particularly as we move away from Angular. That said, this seems like it might be a bit premature.

I did up fixing the specs for op-autocompleter over in #17646 - it was not particularly straightforward (in terms of Dx, ng component testing is pretty painful). However it did help me understand the component and reason about its lifecycle and dependencies.

As a compromise, perhaps we could only delete the specs that are failing/non-trivial to fix? Having extra test coverage usually seems like a good thing to me. A CI job would be nice, but given that the ng test suite runs orders of magnitude faster than our feature specs, running locally is not too difficult.