Feature: mouse keymaps configuration

[Nilsia]

Feature: enable configuration for mouse keys

Extended KeyMaps for MouseEvents.
Added a trait for KeyEvent and MouseEvent, so Keymaps depends on generics.

Updated / Added tests for mouses in configuration.

This is a pull request for this issue : #7982

[the-mikedavis]

I agree with @pascalkuthe that #7982 would be a nice-to-have feature but Helix is keyboard-centric (ref #7982 (comment)). This is a really massive change that we wouldn't be comfortable merging for a low priority issue.

I scanned through the changes though and it looks like the bulk of the changes come from trying to make mouse config and commands roughly equivalent to keyboard config and commands via the trait. The trait is forcing an abstraction that shouldn't exist. You don't need to be able to execute regular commands with the mouse and definitely not execute mouse commands via the keyboard. Instead mouse commands can be separate (for example under a helix-term/src/commands/mouse.rs module) and take additional parameters like the mouse position. The existing commands and keymap structs can be left untouched.

[Nilsia]

Well, I all agree.
I will rework on this, to make these changes:

• Add a new type of commands that are only made for the mouse (some of them will point out to key commands like goto_line_end or move_next_word_end (using the last one makes easier selecting a word)),
• differ Keymaps and Mousemaps where Mousemaps will only accept 2-left = "" and not 2-left = { 1-right = "" }
• the code will maybe be in some ways a bit duplicated, as so I will try to add traits without generics