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

…pensearch-project#1181) (#3)

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

Signed-off-by: Yury-Fridlyand <[email protected]>

* Fix doctest after rebase.

Signed-off-by: Yury-Fridlyand <[email protected]>

* Fix doctest after rebase. - Typo fix.

Signed-off-by: Yury-Fridlyand <[email protected]>

* Update syntax section.

Signed-off-by: Yury-Fridlyand <[email protected]>

Signed-off-by: Yury-Fridlyand <[email protected]>
Signed-off-by: Yury-Fridlyand <[email protected]>

Signed-off-by: Yury-Fridlyand <[email protected]>
Signed-off-by: Yury-Fridlyand <[email protected]>
Co-authored-by: Yury-Fridlyand <[email protected]>