Add capability for creating multiple rows in single query using insert into values (), (), () dialect

[samarpanB]

Suggestion

There is no support for inserting multiple rows in one query which is pretty much a standard of SQL. There is a standard dialect for this too which most of the SQL databases support like mysql, postgres, sqlserver, oracle, etc. Connector should have basic support for this with a flag for enabling/disabling at derived connector types for each database.
There are some databases which does not support it. For that reason, we need the flag.

Use Cases

Bulk create function in juggler will use it. Refer loopbackio/loopback-next#3357

Examples

Optimally, instead of:

INSERT INTO `tbl`(`fld1`,`fld2`,`fld3`,`fld4`) VALUES(1,2,3,4);
INSERT INTO `tbl`(`fld1`,`fld2`,`fld3`,`fld4`) VALUES(10,20,30,40);
INSERT INTO `tbl`(`fld1`,`fld2`,`fld3`,`fld4`) VALUES(100,200,300,400);

We would have:

INSERT INTO tbl(fld1,fld2,fld3,fld4) VALUES(1,2,3,4),(10,20,30,40),(100,200,300,400);

Acceptance criteria

TBD - will be filled by the team.