Add auth modes for authorization

[mootz12]

What problem does your feature solve?

The CLI currently has one default behavior for simulating and signing Soroban authorization entries, and it does not support non-root authorization.

The CLI is a developer focused tool, and therefor users should be able to simulate, sign, and submit transactions with non-root authorization.

What would you like to see?

#2530 adds validation an an approval mechanism for authorization entries. After this is merged:

Add an --auth-mode flag for transaction-producing commands that simulate Soroban transactions before signing and submitting them. Also support the env var STELLAR_AUTH_MODE.

Suggested modes:

• root: default mode. Simulate with root authorization behavior and ask for approval before signing any non-strict authorization entry.
• non-root: simulate with non-root authorization support and ask for approval before signing any non-strict authorization entry.

The existing --auto-sign signing option should continue to skip confirmation prompts, but it should not turn structurally invalid authorization entries into signable entries. Invalid authorization entries should continue to hard-error.

What alternatives are there?

Don't support non-root authorization.

[tupui]

Oh nice! The non-root part would really be helpful. All that would have helped me on #2549