test: share karma config and remove test configs of demo app

[chintankavathia]

share common karma config and also remove test config of demo app as there are no tests.

What kind of change does this PR introduce? (check one with "x")

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior? (You can also link to an open issue here)

What is the new behavior?

Does this PR introduce a breaking change? (check one with "x")

• Yes
• No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:

[spike-rabbit]

I am in favor of deleting unused configurations, but I don't see that we need the shared file.
I don't think we are planning to introduce unit tests for the demo. @fh1ch opinion?

[fh1ch]

I am in favor of deleting unused configurations, but I don't see that we need the shared file. I don't think we are planning to introduce unit tests for the demo. @fh1ch opinion?

@spike-rabbit I'm 100% with you on this one. Deleting the unit-test configuration as well as the Angular CLI cfg for it makes absolutely sense, we currently don't plan to introduce any unit-test for the demo and I frankly also can't think of any valid use-cases in doing so. But I also don't think we need a shared file nor deviate from Angular here, since we should anyway move to Vitest in the mid-term. But maybe I also lack context, since What is the current behavior?/What is the new behavior? was not provided.