Avoid unnecessary transform resets for pixel snapping

[flar]

During some new development work that might make transform resets more expensive we realized that the resets were mostly coming from the calls to snap the transform to a pixel translate value and many of those were NOPs since the transform was already on a pixel translate value. This PR will avoid those trivially unnecessary reset operations.

[flar]

Discovered while working on https://github.com/flutter/engine/pull/50935

[flar]

There were added to fix problems we had with not maintaining full 4x4 transforms during the layer recursion so they are tested someplace indirectly. But, I could add some LSS/DlMCT tests to test them more directly.