This diff introduces the keyserver selection settings panel in user settings. This diff just introduces the element, and subsquent diffs will handle all the navigation/onPress logic
Figma designs:
Linear task:
https://linear.app/comm/issue/ENG-4714/create-new-keyserver-selection-setting-panel-in-the-user-settings
https://linear.app/comm/issue/ENG-4912/gate-keyserver-selection-setting-panel-behind-staffcansee-flag