[Tracking] Replace InputSimulator with alternative in tests to make them reliable.

Tracking issue for:

1. While investigating flaky tests, we found that some of the operations around Cursor and Mouse are interfering with other tests that run in parallel. Until we separate them into their own collection, we are making unit tests run sequentially.

2. Vsplit and Hsplit static cursors have issues with disposing inconsistently. Currently, these two cursors are excluded from tests but need investigation to enable them back.

3. Also, while investigating flaky tests that perform operation on the UI, we found InputSimulator used in tests is not reliable in clearing the input message queue and ensuring the operation is successfully performed. InputSimulator is a third party NuGet we use in tests and does not carry any support for the issues we encounter with it.

This issue is going to track the work need to run tests in parallel once we fix these reliability issues.