[1.7.x] Fixed #23817 -- Updated docs on QuerySet evaluation

Removed inaccurate info about partial evaluation after refs #18702.
Added information on modifying sliced QuerySets; refs #22503.

Backport of 327df551e89a505c5756becee97c40198f38aff2 from master
[1.7.x] Added missing backticks to form validation docs

Backport of 38ab0f13fac428dd05dad02ef7c94da5035927ad from master
[1.7.x] Fixed #23605 -- Fixed nested subquery regression

Added relabeled_clone() method to sql.Query to fix the problem. It
manifested itself in rare cases where at least double nested subquery's
filter condition might target non-existing alias.

Thanks to Trac alias ris for reporting the problem.

Backport of 5c481db29572a387651681b43d5d4523f96b3793 from master
[1.7.x] Fixed duplicate index error on Oracle; refs #23859.

Refers to regression introduced in 7b4a994599b75a07cb07d1e0cc26b3bbf25ab7a6

Backport of 4c709cc0ef0daa2b527e056865f51796fb0d42f3 from master