17914 Fix child caching in opacity_layer (cla: yes, perf: speed, severe: performance)

18132 Revert again “Remove layer integral offset snapping” (cla: yes, perf: speed, severe: performance, waiting for tree to go green)

18225 Setup default font manager after engine created, to improve startup performance (cla: yes, perf: speed, severe: performance, waiting for tree to go green)

18255 Restore integer snapping on OpacityLayer (cla: yes, perf: speed, severe: performance)

18439 Roll buildroot to flutter/buildroot@a4f3c4d5023e080ee50596e6623d179e9c5f839b (cla: yes, perf: app size, perf: speed, severe: performance, waiting for tree to go green)