Remove redundant prerequisite steps from the default optimizer sequence

[cameel]

Since gho steps are hard-coded as prerequisites, there's not much point in having them in the default sequence. All other steps are supposed to preserve these properties.

For now this is just to verify that removing them does not really change generated bytecode in a meaningful way.

If this is true, we might consider merging it, though that would probably be better done only after rebasing it on the new sequence (#15030). Otherwise merging it would just revert it.

[cameel]

Rebased on top of the new sequence.

[r0qs]

We also need to update the docs with this new default sequence, right? I guess we mention it there.

[cameel]

No, we don't really document the default sequence.

We need a changelog entry though.

[cameel]

This is now ready to be merged. Originally I wanted to do some more testing here to be absolutely sure this does not break anything, but since there are absolutely zero changes in test expectations, I guess I was being too cautious. Conceptually this is just a refactor that should have no user-visible effects, because these steps are still there, before the main sequence.

[rodiazet]

LGTM. Some questions added to clarify.

[rodiazet]

Should we name them?

[cameel]

I didn't because I did not think it was all that relevant to the user. If you do not use a custom sequence, you do not have to do anything. If you do and want to have the default sequence with just some modifications, you have to look at the diff anyway. We do not document the exact shape of the default sequence anyway.