[Performance] Add flutter_gallery__transition_perf benchmarks of the new Flutter gallery app

[guidezpl]

See flutter/samples#309

Migrated from material-components/material-components-flutter-gallery#559

[liyuqian]

@guidezpl : do you have another issue that tracks monitoring new Flutter gallery app's performance in end-user devices (e.g., through https://firebase.google.com/docs/perf-mon), or is that effort also tracked under this issue?

[rami-a]

I believe this is being tracked here:

#69

[guidezpl]

flutter/flutter#55181 closes this