Additional Postgresql JSON Functions

[hackedXD]

Added more JSON filter functions under postgresql.

Description

Added most of the normal query API's to postgres's contrib json functions. Everything except for search command has been added along with tests.

Motivation and Context

It solved the lack of the ability to query the values inside of json functions, leading to less support for different queries. Issue #1206 Solved

How Has This Been Tested?

I wrote a pytest for my all JSON functions implemented. I created a simple Model with a JSONField, and tested each operation. Does not affect other parts of code

Checklist:

• [ X] My code follows the code style of this project.
• [ X] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added the changelog accordingly.
• [ X] I have read the CONTRIBUTING document.
• [ X] I have added tests to cover my changes.
• [ X] All new and existing tests passed.