ProjectFolder Object Needs a .files Attribute

[utkonos]

What is the feature you'd like to have?
A ProjectFolder object needs a .files attribute that returns a list of ProjectFile objects in the folder.

Is your feature request related to a problem?
Getting this list of files is not trivial without this.

[negasora]

Added in 5.3.8673-dev:
Python: ProjectFolder.files, Project.get_files_in_folder()
Rust: ProjectFolder::files, Project::get_files_in_folder()
C++: ProjectFolder::GetFiles(), Project::GetFilesInFolder()

[utkonos]

@negasora Thanks!! This also covers issue #7685

I'll close that one.