Disallow unquoted literals in LIKE clause in DESCRIBE statement (o…

…pensearch-project#1181) (opensearch-project#3)

* Allow quoted literals only in `DESCRIBE` and `SHOW` clauses. Tests.

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>

* Fix doctest after rebase.

Signed-off-by: Yury-Fridlyand <yury.fridlyand@improving.com>

* Fix doctest after rebase. - Typo fix.

Signed-off-by: Yury-Fridlyand <yury.fridlyand@improving.com>

* Update syntax section.

Signed-off-by: Yury-Fridlyand <yury.fridlyand@improving.com>

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
Signed-off-by: Yury-Fridlyand <yury.fridlyand@improving.com>

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
Signed-off-by: Yury-Fridlyand <yury.fridlyand@improving.com>
Co-authored-by: Yury-Fridlyand <yury.fridlyand@improving.com>