feat(document_change): extract nvim_input from document change

[theol0403]

Ref: #1266

This removes the need for the custom dot repeat hack and composite escape. For composite escape to work it currently needs https://github.com/max397574/better-escape.nvim.

I'm not sure if this is a viable option, just due to edge cases and bugs. However, worth investigating.

Todo:

• handle moving cursor (like with auto parens)
• ignore document changes while in insert mode?
• consider what happens with pasting a line of code containing a composite escape
• try to remove need for better-escape (use vscode cursor instead, and ignore large movements)
• simplify code
• isolate situations where nvim_input is used

[xiyaowong]

Will close this PR. It's a good idea, but it won't work:

1. Performance issues. Any modifications from vscode such as paste, formatting, revert, etc., are split into inputs, undoubtedly causing significant performance issues.
2. Edge cases:
   • What happens if a user pastes text containing a map key sequence in insert mode, how to handle it? (Very difficult)
   • What if the user has other input during insertion?
   • Dotrepeat no longer works correctly, undo stacks in nvim and vscode may be corrupted.
   • Multiple cursor editing in vscode.
   • Modifications from external sources, multiple documents being modified simultaneously, modified buffers not being the current buffer.
   • etc.

Furthermore, the issues that this PR attempts to address are currently quite minor.