test(lsp): refactor and tidy

- Merge all the top level 'LSP' describe blocks
- Refactor text edit tests
- Fix typing errors
- Add linebreaks between tests

.luacheckrc

@@ -42,6 +42,7 @@ globals = {
 }
 
 exclude_files = {
+  'test/_meta.lua',
   'test/functional/fixtures/lua/syntax_error.lua',
   'runtime/lua/vim/treesitter/_meta.lua',
   'runtime/lua/vim/_meta/vimfn.lua',