SystemUI: Add support for udfps dim layer

Oplus decided to use a custom UDFPS implementation where the dim layer
and pressed icon layer aren't controlled by the kernel. Stock Oplus
toggles HBM based on show/hide of the UDFPS overlay instead of touch
event. Thus, a dim layer is created, where the appropriate level of
dimming based on the brightness level is applied.

Oplus uses this implementation for most devices starting from
SM8450 to at least up to SM8650, with the very latest ones
being the exception, where they have switched to LHBM.

Concomitant changes are also made to SurfaceFlinger to pass the magic
Z-order value so that the HBM is engaged. While bitwise operations
ensure that HBM is engaged one way or another, not enabling HBM
before touchdown results in noticeably slower fingerprint operations
compared to those of relatively older devices.

Applying dim also modifies the colors of the UI elements to a slighly
darker shade, more so on low brightness conditions.

Change-Id: I6e3032dd2b4b4b7018c7d6abf27d7e4e6c089896