[Feature Request] Handle Android SOURCE_HDMI CEC remotes generically

Feature request

Handle Android HDMI-CEC key events as a generic navigation source instead of
requiring a fictitious joypad autoconfiguration profile.

Tested environment

• RetroArch 1.22.2_GIT, 32-bit Android build.
• Android 10 / API 29 TV box, Allwinner H616.
• HDMI-CEC confirmed with two Sony 3D televisions:

Both sets send D-pad Up/Down/Left/Right, D-pad Center, and Back. Android
delivers them in this form:

KeyEvent(
  deviceId=-1,
  source=0x02000001 (SOURCE_HDMI),
  scanCode=0,
  keyCode=23
)

The other observed keycodes are standard Android keycodes 4 and 19–22.

Why a controller profile cannot represent this

deviceId=-1 is a framework-injected virtual event. It has no stable physical
device name, vendor ID, or product ID, while RetroArch joypad autoconfiguration
selects profiles by the exact name/VID/PID triple.

Creating a Virtual profile would be unsafe because it could also capture
unrelated synthetic input. Creating Sony-model profiles would be inaccurate:
both televisions arrive through the same anonymous SOURCE_HDMI path.

Current RetroArch master documents CEC as a Virtual device inside the
NVIDIA SHIELD-specific block in input/drivers/android_input.c, but there is
no generic source-specific path for SOURCE_HDMI.

Requested behavior

Please consider one of these source-specific approaches:

1. Route SOURCE_HDMI key events to the Android keyboard/navigation port, so
   normal RetroArch key bindings handle arrows, Enter/Center, and Back.
2. Expose a dedicated synthetic identity such as Android HDMI-CEC Remote,
   selected by event source rather than by the generic Virtual device name.

Either approach should key off SOURCE_HDMI, not TV model or Virtual.
Android's framework already translates the CEC UI-command set to Android
keycodes; the set of buttons received depends on what each TV transmits.

Reproduction/evidence

1. Enable HDMI-CEC on an Android TV device and either tested Sony television.
2. Focus RetroArch and press the television remote arrows, OK, and Back.
3. Inspect Android's recent input queue with dumpsys input.
4. Observe deviceId=-1, source=0x02000001, scanCode=0.
5. Try to create a controller profile: there is no physical device identity
   that can be represented without colliding with unrelated virtual input.

No existing RetroArch issue matching SOURCE_HDMI, Android CEC, or
HDMI remote Android TV was found before filing this report.

Start in input/drivers/android_input.c, especially the existing CEC handling in the NVIDIA SHIELD-specific block, and trace how Android key events are classified and routed. Reproduce the SOURCE_HDMI events with the listed D-pad and Back keycodes, then verify that generic Android HDMI-CEC input works without matching a Virtual or TV-specific controller profile.