Ensure that button touch targets are at least 48x48 dp.

This is to comply with a11y requirements. Buttons affected:
- Connect Device button. Touch height: 32dp -> 48dp.
- Add / Remove to a group button. Touch width and height: 40dp -> 48dp.
- Ongoing Session (Jam) button. Touch width and height: 40dp -> 48dp.

Fix: 409006700
Fix: 409007076
Fix: 409009226
Flag: com.android.media.flags.enable_output_switcher_redesign
Test: atest
SystemUIGoogleScreenshotTests:com.android.systemui.media.dialog, with
Accessibility Scanner app.

Change-Id: I6fe04b67f35c630a0b379ca1c4e9b3a74062e92e