Add --copy-file for remote-run

[Qmando]

Add the ability to copy individual files into remote-run pods into /tmp. This covers a lot of use cases while still making it hard to modify code or copy whole directories.

$ paasta remote-run start -c norcal-devc -s redshift_credentials -i main --interactive --copy-file ~/test1 --copy-file ~/test2
Triggered remote-run job for redshift_credentials. Waiting for pod to come online...
Status: Pod not ready
Pod ready, establishing interactive session...
INFO: You are using an Okta authenticated kubectl wrapper
nobody@remote-run-qlo-redshift--credentials-main-d67jb:/code$ cat /tmp/test1
test
nobody@remote-run-qlo-redshift--credentials-main-d67jb:/code$ cat /tmp/test2
foo

$ paasta remote-run start -c norcal-devc -s redshift_credentials -i main --interactive --copy-file ~/test27657
Triggered remote-run job for redshift_credentials. Waiting for pod to come online...

Pod ready, establishing interactive session...
Error copying file to remote-run pod:
INFO: You are using an Okta authenticated kubectl wrapper
error: /nail/home/qlo/test27657 doesn't exist in local filesystem

[piax93]

This can probably be just a simple execution via subprocess since it does not involve an interactive CLI, and that will also give better error handling compared to the pseudo-terminal contraption I implemented in run_interactive_cli