[pgAdmin4] [Patch] Implementation of the Data Grid and Query Tool

Hi All

I have implemented the Data Grid and Query Tool as one component.

*Functionality working for Data Grid*:

- Add/Update/Delete rows if object is editable.
- Copy row
- Paste row
- Refresh
- Client Filter provided by the Backgrid.
- Filter (User specified, By cell Selection, Exclude Selection
- Add Limit to the query result
- Download the data as CSV.

*Todo's for the Data Grid*:

- Find a way to select backgrid cell when rows are not editable. If
backgrid rows are not editable then Filter by selection and Exclude
selection won't work

*Functionality working for Query Tool*:

- Execute sql query.
- Execute the Highlighted sql.
- Cancel the running query.
- Download the data as CSV

*Todo's for the Query Tool*:

- Open as SQL file.
- Save to SQL file.
- Auto Commit/ Rollback.
- Output Panel should be resizable, so that user can

Attached is the patch file. Please review it and let me know the review
comments if any.

--
*Akshay Joshi*
*Principal Software Engineer *

*Phone: +91 20-3058-9517Mobile: +91 976-788-8246*