45649 [flutter_tool] add a vmservice API for hot ui requests (cla: yes, framework, tool)

45652 Sample driver test working on Fuchsia (cla: yes, d: examples, team, tool)

45654 Fixed incorrect offsetting when applying ShaderMasks (a: quality, cla: yes, framework, waiting for tree to go green, will affect goldens)

45658 Clean up some things I noticed while doing another change (cla: yes, framework, waiting for tree to go green)

45659 Roll engine 27fa60793bcb..5250d6315e7a (4 commits) (autoroller: commit, cla: yes)

45663 Roll engine 5250d6315e7a..2c0eee43923f (2 commits) (autoroller: commit, cla: yes)