Add formatter helper for file extensions filters

[vkbo]

Summary:

This PR adds a helper function for building file extension filters for file dialogs. Aside from not having to generated this special format in multiple places in the code, it also combines the translation strings for the ones used multiple places into a single lookup dictionary, preventing duplicate translation entries.

Related Issue(s):

Reviewer's Checklist:

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All flake8 checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed