[pgAdmin][patch] Utilities for porting pgAdmin tools to React

Hi Hackers,

I have been working on porting the query tool to React. Most of the work is done, but it has hit a snag because of few feature shortcomings of an underlying library. I will be working on it and will send a PR. But, I have also written a good amount of code around the new query tool to help it port faster. That can help to port other pgAdmin tools as well.

So, attached is the patch to help port pgAdmin tools faster and to define standard way of writing the tools in pgAdmin. One can refer the query tool implementation here - https://github.com/adityatoshniwal/pgadmin4/tree/master/web/pgadmin/tools/query_tool

Query tool patch will come soon later.

Please review.