lsp: only show diagnostic once for each line if cursor is not moved

This will help use to check signature help without it being overwritten
by diagnostic popups.

lua/config/lsp.lua

@@ -31,7 +31,19 @@ local custom_attach = function(client, bufnr)
         source = 'always',  -- show source in diagnostic popup window
         prefix = ' '
       }
-      vim.diagnostic.open_float(nil, opts)
+
+      if not vim.b.diagnostics_pos then
+        vim.b.diagnostics_pos = { nil, nil }
+      end
+
+      local cursor_pos = vim.api.nvim_win_get_cursor(0)
+      if (cursor_pos[1] ~= vim.b.diagnostics_pos[1] or cursor_pos[2] ~= vim.b.diagnostics_pos[2]) and
+        #vim.diagnostic.get() > 0
+      then
+          vim.diagnostic.open_float(nil, opts)
+      end
+
+      vim.b.diagnostics_pos = cursor_pos
     end
   })