surfaceflinger: add more setPosition tests

Add LayerTransactionTest.
  SetPositionBasic
  SetPositionRounding
  SetPositionOutOfBounds
  SetPositionPartiallyOutOfBounds
  SetPositionWithResize
  SetPositionWithNextResize
  SetPositionWithNextResizeScaleToWindow

LayerTransactionTest and LayerUpdateTest also have these differences

 - every pixel, rather than a single pixel, of a layer is checked
 - no concept of FG and BG layers with implied coordinates; layers
   are explicitly created, filled, and positioned

Test: SurfaceFlinger_test
Change-Id: Iee4818766e9f218391f869490d49ab5e54a80a49