fix(actions): rework copy and move

[TheBlob42]

• streamline copy, move, delete and rename
• group together them inside the 'actions.lua' file
• catch edge cases for overwriting
• use lstat to better handle links
• catch for vim.fn.inputlist

This is a rather big restructure, but I am testing this now for quite some time. It should fix several issues and catch certain edge cases (e.g. copy a directory to a folder where a file with the same name already exists). In a future step it probably makes sense to extract those "file actions" into its own file, but that is the task for another refactor