* css: Extract invalid input outline and shadow colors to variables.
We will use these colors in future for input pills and it would be
convenient to have them in a variable.
* group_setting_pill: Show outline on invalid input.
We could have manipulate the class directly from user_group_pill. But
it felt better to have `show_outline_on_invalid_input` as a param for
the input_pill prototype since we can have a consistent error state for
other pill input boxes if we want to.
* input_pill: Widget should not show as pending after pill creation.
* group_settings: Disable save changes button if pill widget is pending.
This will disable the button for group, realm and stream group settings.
* user_group_create: Don't go to next step with pending group widget.
We just show the red outline and shaking animation as an indication that
a group widget setting is pending when the user tries to go to the add
members step.
* stream_create: Don't go to next step with pending group widget.
Fixes#32113.
We just show the red outline and shaking animation as an indication that
a group widget setting is pending when the user tries to go to the add
subscribers step.
