Refactor all signing to go through the same code path

[elizabethengelman]

Currently there are 2 code paths to sign a tx:

1. using config::sign_with::Args.sign_tx_env which gets a Secret from locator.get_secret_key, and then gets the signer using secret.signer(). This path works for secure store, because it isn't trying to reveal the secret key.
2. using config::Args.sign / config::Args.sign_with_local_key
   • this currently isn't working on main because it is trying to use Secret.private_key
   • in Fix signing with a secure store key #1982 this should be fixed, and uses a similar path to done #1656

It will be easier to maintain this if there is only one path for signing, so that's what this issue is for.

[github-actions]

This issue is stale because it has been assigned for 30 days with no activity. It will be closed in 90 days unless the stale label is removed, and the assignee is removed or updated.

[github-actions]

This issue is stale because it has been assigned for 30 days with no activity. It will be closed in 90 days unless the stale label is removed, and the assignee is removed or updated.