Turn Advanced settings into a navigable page, like Certificates (#311)

Replaces the "Show advanced settings" toggle + a group gated by
visible: () => this.showAdvancedSettings with a type: "page" entry
nested in "Settings", matching how "Certificates" already works.
Drops the showAdvancedSettings instance field and its getControlValue/
setControlValue cases entirely -- a page doesn't need a persisted (or
even session-only) reveal flag, since navigating into it is itself the
deliberate action that used to require flipping the toggle first.

Also fixes the same setting.settingEl.remove() + group.listEl render
bug in the "License" item (same root cause fixed elsewhere for
Connection information / Certificate status) while moving it into the
new getAdvancedSettingDefinitions() method, so this doesn't ship a
known-broken render callback in restructured code.

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>