feat(pycharm): add configuration screen with variable, environment variables and testsuite file support

[hasanalpzengin]

Related with the Task #417

This update introduces a visible and functional configuration for test items, enhancing the overall usability of the PyCharm plugin:
Adds new fields to the configuration page for PyCharm:

• environment variables: to pass into the commandline interface as environment variable if given.
• variables: robot variables that will be passed to the execution with -v flag. Seperated with comma following the format:
  key1=value1,key2=value2 if given.
• additional arguments: any arguments that can be passed to the execution if given.
• suite path options: suite path to select. It will be converted to TestItem and added to the execution with --by-longname if given.

UI View:

[d-biehl]

Sorry for the late reply, I needed some vacation from RobotCode ;-)
But, your PR looks really good!!! I need a little more time to take a closer look at it though.
What I do notice is that I would like to be able to execute individual test cases, not just one, and not just complete robot files. This already works, but it is not yet possible to select the test cases in the RunConfig. Maybe you can find a solution?

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[hasanalpzengin]

@d-biehl multiple testcases would already be available with comma seperation in includedTestItems field. However maybe it's a problem of UX, therefore I have changed the field to a CheckBoxList from Jetbrains library for a modern look:

However I ask for your opinion about the test suite field. Would you like to keep it or remove it and leave all decision to the Test Items checkbox list ?
Currently both fields remains this means:
if you select a test suite path. We'll only run the tests from this file. However it makes the usage of Test Items list a bit obsolete because if the path is selected, all tests in the given suite path is appended to the selection no matter if they were selected or not.