Closes #2150

Previously, we ignored the --project arguments passed to the sentry-cli deploys new command. Regardless of whether any --project was provided, the deploy was created for all projects associated with the given release.

Now, we respect the --project argument. If provided, we only create the deploy for the project(s) specified. If omitted, the deploy is created for all projects associated with the release, as previously.

Fixes #2156

Also, use `Cow` in the struct to avoid allocations

Fixes #2155

Fix a bug where a failure in sending the crons checkin before running the program in the monitors run command (e.g. due to a Sentry outage) would cause the program to be prevented from running. Now, we instead log the error and continue running the program.

Also, ensure that a failure in sending the final checkin (after the program has finished) does not cause the program to exit with a different exit code. sentry-cli monitors run should propagate the exit code of the program it runs.

Fixes #2169

Reverts #2158