Determine and document CLI config vs env precedence

[mootz12]

What problem does your feature solve?

We should consider making CLI config values (stellar network/keys/fees use) take precedence over env values.

Currently, it goes as follows:

1. args
2. env
3. CLI config

Context: #2321 (comment)

What would you like to see?

For precedence to be:

1. args
2. CLI config
3. env

What alternatives are there?

Leave it as is.

[tupui]

Linking #2271 too. I also had some suggestions.

[leighmcculloch]

Could you elaborate on the problem that caused this issue? The context link doesn't seem to work for me.

I think it would be surprising to place env after config in the order of precedence.

Are there examples of other CLIs doing that?

Env is something that can be controlled for a single command inline in a script, which is a common pattern, so it should take precedence over user/system config. I believe many CLIs work this way.