treewide: language refactor

[NotAShelf]

Very breaking change that moves formatter and diagnostic configurations to their standalone plugin/module counterparts for extended modularity. The new idea is that formatters/diagnostics are provided as module options, which are enabled by any language modules that need it. This allows for users to opt out of specific language modules, but still provide appropriate support for their desired languages.

This should improve configurability, compatibility and performance that were all impacted negatively by null-ls.

1. Adds conform.nvim and nvim-lint plugins for formatting and linting respectively.
   • Document adding formatters and linters (add documentations for vim.languages.*.extraDiagnostics  #239)
2. Deprecates null-ls, and removes any configuration that depends on null-ls (WIP)
3. Streamlines addition of new LSPs/formatters and so on.