feat: support JSON_VALUE(j, '$.a' RETURNING CHAR(50))

[cyjake]

It looks like the performance of querying properties in native JSON data type in MySQL can be boosted with specific index, as long as the index is created with JSON_VALUE(field, path RETURNING type) that casts the property value to certain type.

To enable this optimization, the expression parser and formatter in Leoric needs to be updated, hence proposed this pr.

• https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-21.html#mysqld-8-0-21-json
• https://dev.mysql.com/doc/refman/8.0/en/json-search-functions.html#function_json-value

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (55539b6) 96.66% compared to head (e162157) 96.70%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #414      +/-   ##
==========================================
+ Coverage   96.66%   96.70%   +0.03%     
==========================================
  Files          45       45              
  Lines        3627     3668      +41     
  Branches       72       72              
==========================================
+ Hits         3506     3547      +41     
  Misses        106      106              
  Partials       15       15              

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[JimmyDaddy]

LGTM