ENH: Add auto_focus and pattern to form_elements/form_panel

Summary

Moves code from customer custom scripts to webui:

1. Adds "pattern" option for text fields (module form_elements)
2. Adds "auto_focus" parameter to form_panel module

Focus

Both features mentioned above are independent. They just happened to be developed simultaneously.

Test Environment

1. See unit tests.
2. Manual testing: Start the webui and execute this in the console:

  var form_config = {
    fields: [{
      name: "test",
      type:"text",
      pattern: "[0-9A-F]+",
      required: true,
    },]
  }
  var cb = form_panel.create_show_form_callback("some_id", "Title", form_config);
  navbar.add_tool("test", "toolbox", {callback: cb});

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