SurfaceFlinger: retain the sideband layer information for composition

when present, the sideband layer stream information is not saved into
the BufferQueueLayer::mSidebandStream, during "latchSidebandStream".

this subsequently leads to such layer being marked as non visible in the
composition stack and to be drop from advertisement to hardware composer
even though a sideband layer is defined in the rest of the framework.

this seems to be a regression introduced during android 9 to android 10
revamp of the SurfaceFlinger for buffer latching.  latching a sideband layer is actually harmless since there is no buffer associated with it that need to be waited on from the gpu side.

the fix proposed here allows to maintain the knowledge of the sideband
layer and make it visible in the composition stack for hardware composer to handle adequately.

for illustration purposes, the relevant snippet of the layer composition
stack are posted here from "dumpsys SurfaceFlinger", highlighting the
issue with ">>>".

[before]:

* compositionengine::Layer 0xa959b34c (SurfaceView - <truncated>)
    frontend:
      isSecure=false geomUsesSourceCrop=false geomBufferUsesDisplayInverseTransform=false
               geomLayerTransform 0x00000000 (ROT_0 ) 0x00 (IDENTITY )
    1.0000  0.0000  0.0000
    0.0000  1.0000  0.0000
    0.0000  0.0000  1.0000

      geomBufferSize=[0 0 -1 -1] geomContentCrop=[0 0 -1 -1] geomCrop=[0 0 -1 -1] geomBufferTransform=0
        Region geomActiveTransparentRegion (this=0xa959b3f8, count=1)
    [  0,   0,   0,   0]
      geomLayerBounds=[0.000000 0.000000 0.000000 0.000000]
      blend=INVALID (0) alpha=1.000000
>>>   type=0 appId=0 composition type=INVALID (0)
      buffer: buffer=0x0 slot=-1
>>>   sideband stream=0x9b509900
      color=[0 0 0]
      dataspace=UNKNOWN (0) hdr metadata types=0 colorTransform=<truncated>

[after]:

* compositionengine::Layer 0xa9a5034c (SurfaceView - <truncated>)
    frontend:
      isSecure=false geomUsesSourceCrop=true geomBufferUsesDisplayInverseTransform=false
               geomLayerTransform 0x00000000 (ROT_0 ) 0x00 (IDENTITY )
    1.0000  0.0000  0.0000
    0.0000  1.0000  0.0000
    0.0000  0.0000  1.0000

      geomBufferSize=[0 0 -1 -1] geomContentCrop=[0 0 -1 -1] geomCrop=[0 0 1920 1080] geomBufferTransform=0
        Region geomActiveTransparentRegion (this=0xa9a503f8, count=1)
    [  0,   0,   0,   0]
      geomLayerBounds=[0.000000 0.000000 1920.000000 1080.000000]
      blend=NONE (1) alpha=1.000000
>>>   type=1 appId=10064 composition type=SIDEBAND (5)
      buffer: buffer=0x0 slot=-1
>>>   sideband stream=0x9a1472b0
      color=[0 0 0]
      dataspace=UNKNOWN (0) hdr metadata types=0 colorTransform=<truncated>

Bug: 140128098
refs #SWANDROID-6178

Signed-off-by: Pierre Couillaud <pierre.couillaud@broadcom.com>