Permissions Flags: Merge SkinTemp/Spo2/Replace BodySensors flags.

The team plans to release the BodySensor deprecation alongside bringing the skin temp and spo2 permissions to the platform. Rather than coordinate across multiple flags, just rely on the single point of control.

- Updates the description of replace_body_sensors flag to include skin temp and spo2.
- Consolidates flag usage on replace_body_sensor...
- Deletes the SpO2 and SkinTemp flags. This should be safe since no one is using these externally yet at this point.

Bug: 364640981
Change-Id: I3f54953a8f5de7fd7ea84ea91d814963647506ab
Flag: android.permission.flags.replace_body_sensor_permission_enabled
Test: Presubmits