Feature to Change component after adding element to testplan

[rollno748]

Description

This will allow user to change element after adding it to the testplan
The components which are enabled with this feature are

1. Config element
2. ThreadGroup
3. Sampler
4. Listener
5. Timer
6. Assertion

Motivation and Context

It was quite annoying to change the threadgroup or other component after adding it to the testplan

How Has This Been Tested?

Screenshots (if appropriate):

Config Element:

Thread Group:

Sampler:

Listener:

Assertion:

Timer:

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

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