Initial gtk4 migration

[ochibani]

I tried to minimize code changes it's not working yet, but can be a good starting point. The window size is not the same as the gtk3 version, probably something wrong in main.ui file. FileChooserButton not the same as the gtk3 we can make it look and act the same as old version, but I don't think this is useful. We need to replace Appindicator

[xlmnxp]

I suggest to remove libappindicator support

[xlmnxp]

feature (#37): included in this PR

[ochibani]

I believe we need to do this tasks to have working X11 version. Stable X11 version:

• [x] Fix progress dialog (“not doing its job correctly”).
• [x] Fix play button (“xdg-open return no such file or directory”).
• [x] Fix some Gtk messages related to “main.ui”.
• [x] Fix is_file_already_exists function.
• [x] Return missing video formats to combo box.(Not really fixed)
• [ ] A̶d̶d̶ i̶n̶d̶i̶c̶a̶t̶o̶r̶ f̶u̶n̶c̶t̶i̶o̶n̶a̶l̶i̶t̶y̶.(dropped)
• [x] Add timer to header bar.

[xlmnxp]

@ochibani I fixed colors of button select and area selector to use theme colors

[ochibani]

Select a Window is not supported in Wayland due to security measures.

[xlmnxp]

@ochibani that wired I know discord, slack, brave and others support select window

[ochibani]

Audio recording not working in old version gtk3 due to how record button function works, so I removed the audio only record functionality as it's not core functionality for blue recorder.

[xlmnxp]

@ochibani don't merge, still there issue with Clone derive for Std::Process::Child

[xlmnxp]

Thank you, I will merge your changes