Contains fixes requested in the issue (and some tiny extras), together with analysis why they don't affect the users (see commit messages).
Fixes [ #11800](https://github.com/scylladb/scylladb/issues/11800)
Closes#11926
* github.com:scylladb/scylladb:
alternator: add maybe_quote to secondary indexes 'where' condition
test/alternator: correct xfail reason for test_gsi_backfill_empty_string
test/alternator: correct indentation in test_lsi_describe
alternator: fix wrong 'where' condition for GSI range key
(cherry picked from commit ce7c1a6c52)
0debb419f7