[pgAdmin4][Patch]: Feature #4202 Implement new framework to test Reverse Engineering SQL

Hi Hackers

I have implemented the new test framework to test the Reverse Engineering
SQL. I have integrated it as a part of API/Regression test suite. It will
work when we run all the test cases or module wise test case.

*How it works*: Attached patch contains the generic framework to read all
the JSON files from the *tests->version based (example 9.6_plus, 10_plus or
default) folder. *Run all the test scenarios present in the JSON file in
sequential order.

Format of the JSON file is mentioned in
"<path_of_source>web/pgadmin/browser/server_groups/servers/databases/casts/tests/default/test.json"

For expected SQL we will have following two options:

- Provide the expected sql in scenario itself as parameter *"expected_sql"
: "<SQL>"*.
- Create a output file with any name in the same directory where the
JSON file resides and specify the parameter "*expected_sql_file": "<name
of the file>"*

Attached patch contains both the above mentioned examples.

Please review it.

--
*Thanks & Regards*
*Akshay Joshi*

*Sr. Software Architect*
*EnterpriseDB Software India Private Limited*
*Mobile: +91 976-788-8246*