use top level --org when subcommand -org is not used.

[alexcb]

What existing functionality needs improvement?
earthly has both a top-level --org as well as some commands have a different --org option under the subcommand, for example:

earthly --org=not-this-one secret --org=this-one ls
Error: not a member of org "this-one"

will only use the secret's --org value, and when omitted (e.g. earthly --org=not-this-one secret ls) falls back onto the automatic org detection heuristic

Expected Behavior
Before falling back on the automatic org detection heristic, earthly should attempt using the top-level value of --org=not-this-one.

Expected Examples:

earthly --org=not-this-one secret --org=this-one ls
Error: not a member of org "this-one"

earthly --org=not-this-one secret ls
Error: not a member of org "not-this-one"