Screen Capture: Create primary icon button in Compose

Creates a primary button with text and an optional leading icon in
Compose. The button text and icon are both parameterized. This is
suitable to be used as an action button for capturing the screen.

Screenshot: http://screen/9nSbxzgkenvGEnk.png

Bug: 412723048
Test: Manual
Flag: com.android.systemui.desktop_screen_capture
Change-Id: I229f59dda06249040ae7c22f4615a52a842839a7