Remove deprecated MongoDB test elements

Description

Removed the two deprecated test elements MongoScriptSampler and MongoSourceElement.
Updated tests cases that leveraged these components.
Updated docs
Updated properties
Updated templates
Updated changes.xml

Motivation and Context

Components were deprecated and intended to be removed in version 3.1 according to issue history. No need to add additional external dependencies into JMeter when a MongoDB plugin could be created to support this use case.

How Has This Been Tested?

Updated impacted test cases reran all tests.
Interestingly enough running test from master prior to change resulted in 2107 tests with 353 failures.
Post change there are 2067 tests of which 349 are failures.
Maybe something wrong with my local setup?

Screenshots (if appropriate):

Types of changes

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [ x] My code follows the code style of this project.
• [ x] I have updated the documentation accordingly.