Remove unused methods hitsExecutionNeeded and hitsExecute from FetchSubPhase

[brwe]

The hits execution was never used by any sub fetch phase.

[javanna]

Not sure, they might come handy when we want to address #11223 aka highlight all documents at once. On the other hand we can always restore them or add some similar mechanism when needed in the future. This was also exposed to plugins right? So who knows if any plugins is using this or not.

[brwe]

This was also exposed to plugins right? So who knows if any plugins is using this or not.

We could not plug in fetch phases in so far so I think that no plugin can use this.

Not sure, they might come handy when we want to address #11223 aka highlight all documents at once.

Indeed, it might help there. I also wonder if it might help for #12413 together with the pluggable fetch phases in #12400 . On the other hand I have the feeling that we though 'this might be handy' for four years now...

I am not passionate about it but since it is not a huge improvement and this might be handy at some point, I'll just leave all as is and close the pr again.