Remove unused methods

[litetex]

• I carefully read the contribution guidelines and agree to them.
• I have tested the API against NewPipe.

After working on TeamNewPipe/NewPipe#7458 I noticed that these methods (and corresponding tests) are no longer required and can be removed.

This PR can be merged once TeamNewPipe/NewPipe#7458 is done

[AudricV]

@litetex You should have checked with more caution because they are still used by NewPipe on the dev branch!

> Task :app:compileDebugKotlin
e: [...]/app/src/main/java/org/schabi/newpipe/error/ErrorInfo.kt: (68, 45): Unresolved reference: getNameOfService
e: [...]/app/src/main/java/org/schabi/newpipe/error/ErrorInfo.kt: (76, 45): Unresolved reference: getNameOfService
e: [...]/app/src/main/java/org/schabi/newpipe/error/ErrorInfo.kt: (98, 57): Unresolved reference: getNameOfService
e: [...]/app/src/main/java/org/schabi/newpipe/error/ErrorPanelHelper.kt: (109, 29): Unresolved reference: getNameOfService

> Task :app:compileDebugJavaWithJavac

[...]

[...]/app/src/main/java/org/schabi/newpipe/util/ServiceHelper.java:142: error: cannot find symbol
        final int serviceId = NewPipe.getIdOfService(serviceName);
                                     ^
  symbol:   method getIdOfService(String)
  location: class NewPipe

This PR should be reverted in my opinion.

[litetex]

@AudricV
Thank you for noticing, looks like I overlooked the Kotlin code.

A fix is provided with TeamNewPipe/NewPipe#8531

[TobiGr]

I am a little late on this. Can you please clarify why you removed the methods?
The extractor is not only used by NewPipe, but other applications, too. Removing methods without a prior warning / deprecation is not good practice.
I'd suggest to revert this PR as you already started to move one method into the app.

[litetex]

Can you please clarify why you removed the methods?

1. I thought they were just used inside Moved subscription import/export options to (overflow) menu NewPipe#7458 but apparently I was wrong they were also used on some other places
2. These methods are just shorthand methods for getService with an additional exception-check because somehow getService throws an checked Exception instead of simply returning null which would be a lot better.
3. They are never used anywhere inside the extractor.
4. 
5. The tests are completely pointless
   a. The methods are in in my opinion way to simple to even have tests for
   b. If you write tests don't just write it for one testcase...

Removing methods without a prior warning / deprecation is not good practice.

I think people can handle removal of 2 barely used methods. Especially when the complete extractor architecture was/will be reworked with #810 and #862.

Also there was no prior warning when the behavior of returning null was changed to throwing a exception.

as you already started to move one method into the app.

I moved the method into the app, because a) it's used there and b) the new method doesn't have a use the unnecessary ExtractionException.