ci: add melos bootstrap action #3473

Job	Run time
unit_tests	3m 48s
functional_tests	2m 27s
end2end_test_prep	1m 59s
end2end_test_staging	4m 48s
end2end_test_56	3m 10s
end2end_test_34	2m 54s
end2end_test_12	3m 9s
push_canary_secondary_image	0s
push_canary_virtualenv_image	0s
push_prod_secondary_image	0s
push_prod_virtualenv_image	0s
push_staging_observable_secondary_image	0s
push_staging_secondary_image	0s
push_staging_virtual_env_images	0s
	22m 15s

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