protobuf: automate derived file generation #7534

Job	Run time
1/4	12m 10s
1/4	12m 10s
2/4	13m 16s
2/4	13m 16s
3/4	13m 33s
3/4	13m 33s
4/4	13m 36s
4/4	13m 36s
py-3-latest	23m 17s
py-3-latest	18m 14s
flaky	7m 11s
flaky	7m 11s
_remote_background_indep_poll	23m 9s
_remote_background_indep_poll	22m 59s
_remote_background_indep_tcp	33m 48s
_remote_background_indep_tcp	32m 3s
macos 1/5	34m 14s
macos 1/5	34m 14s
macos 2/5	31m 22s
macos 2/5	31m 22s
codecov	0s
codecov	0s
	6h 44m 14s

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