Refactor project configuration branching

[bugzilla-to-github]

This issue was created automatically by a script.

Bug 1508662

Bug Reporter: @mathjazz

With the introduction of project configuration[1] our code often branches depending on whether project configuration is provided. We should make better use of OOO or look into other techniques to reduce the number of cases like this:

if project_configuration:
// do this
else:
// do that

[1] https://moz-l10n-config.readthedocs.io/en/latest/fileformat.html