Refactoring all-the-icons functions

[wyuenho]

lsp-modeline--code-actions-icon isn't guarded by the proper checks for all-the-icons-octicon function, which will cause all-the-icons to load in the terminal, even though it is not supported. I've also taken the opportunity to refactor the 2 functions that use all-the-icons to use the new lsp-icons-all-the-icons-icon function.