Map MySQL JSON to Presto JSON

[ebyhr]

Implements prestodb/presto#12806

TestPostgreSqlTypeMapping has this test "\"text with \\\" quotations and ' apostrophes\"", but mysql's escape logic is little different from postgresql and presto. Then, I changed the test case to "\"text with ' apostrophes\""

presto> select CAST('"text with \" quotations and '' apostrophes"' AS JSON);
                       _col0                       
---------------------------------------------------
 "\"text with \\\" quotations and ' apostrophes\"" 

postgresql> select CAST('"text with \" quotations and '' apostrophes"' AS JSON);
                    json                     
---------------------------------------------
 "text with \" quotations and ' apostrophes"

mysql> select CAST('"text with \" quotations and '' apostrophes"' AS JSON);
ERROR 3141 (22032): Invalid JSON text in argument 1 to function cast_as_json: "The document root must not follow by other values." at position 13.

mysql> select CAST('"text with \\" quotations and '' apostrophes"' AS JSON);
+---------------------------------------------------------------+
| CAST('"text with \\" quotations and '' apostrophes"' AS JSON) |
+---------------------------------------------------------------+
| "text with \" quotations and ' apostrophes"                   |
+---------------------------------------------------------------+

[ebyhr]

The travis failed by No output has been received in the last 10m0s

[findepi]

@ebyhr thank you for your contribution!
@electrum do you want to have a look?

[electrum]

Merged, thanks!