split TextInputComponent::process_inputs into separate methods

[gim913]

Hello,

I've ~~stolen~~ borrowed the code that handles key combos for tui_textarea to my own project, in the process I've split it into multiple functions:

• process_command_key - handling Ctrl
• process_meta_key - handling Alt
• process_meta_command_key - Ctrl + Alt
• process_non_modded - no modifiers

I'm not sure if this is a good idea, up to you to decide.

I've double checked if all the keys that were handled before this change are also handled afterwards.

Pros:

In my opinion code is cleaner / easier to read:

	fn process_command_key(ta: &mut TextArea<'_>, key: Key) -> bool {
		match key {
			Key::Char('h') => {
				ta.delete_char();
				true
			}
			Key::Char('d') => {
				ta.delete_next_char();
				true
			}

Cons:

repeating functionality occurs in multiple methods:

	fn process_non_modded(ta: &mut TextArea<'_>, key: Key) -> bool {
...
			Key::Left => {
				ta.move_cursor(CursorMove::Back);
				true
			}
...
	}
	
	fn process_command_key(ta: &mut TextArea<'_>, key: Key) -> bool {
...
			Key::Char('b') => {
				ta.move_cursor(CursorMove::Back);
				true
			}

P.S. I've been looking at the project in 2021, it's nice to see how it progressed.

I followed the checklist:

• [x] I ran make check without errors
• [x] I tested the overall application
• [?] I added an appropriate item to the changelog