refactor(lsp): consolidate the different floating window methods into open_floating_preview

runtime/lua/vim/lsp/diagnostic.lua

@@ -1151,6 +1151,7 @@ function M.show_line_diagnostics(opts, bufnr, line_nr, client_id)
     end
   end
 
+  opts.focus_id = "line_diagnostics"
   local popup_bufnr, winnr = util.open_floating_preview(lines, 'plaintext', opts)
   for i, hi in ipairs(highlights) do
     local prefixlen, hiname = unpack(hi)