GD-40: Allow using Mono editor to run GDScript tests

[NaixGames]

gdUnit allows quite easily to run quite easily tests in gdscript on the Mono editor. This includes running and interacting with scenes that might contain C# scripts without the need of using the C# runner. This has some advantages, as test in the editor are easier to run and set, which is useful for quickly setting up projects with collaborators. In that regard it is also convenient that the action can also support running gdscript tests while using the mono editor. However, right now the option godot-net controls both, the type of test getting run and the editor used to run it. So gdscript test wont be run if using godot-net set to true, and setting it to false will cause any test that contains a C# script to fail since the resource wont get properly compiled. This issue is not solvable with the actual flags for the action and it does not reflect the behaviour from the editor.

A solution to this would add a flag to choose to run (or not) the mono behaviour and another one to run C# tests. Lets call the first one godot-net (maintaining the same name as before) and the second one tests-net. The first flag is use on the action to decide which editor is used (which I think is lines 68, 88 and 136) and the second one to decide which tests are run (which I think are lines 168, 185, 194 and 210). However, I dont know if this would cause any other issue.