[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.

--
Thanks,
Aditya Toshniwal
pgAdmin Hacker | Software Architect | *edbpostgres.com*
<http://edbpostgres.com>
"Don't Complain about Heat, Plant a TREE"