Allow user to define safe nonce when connected to a safe as an owner

[auryn-macmillan]

Is your feature request related to a problem? Please describe.
When connected to a safe as an owner, if there is a pending transaction in the safe transaction service, then Pilot adds transactions at the next available nonce. There is no way to manually define the nonce in Pilot.

Describe the solution you'd like
When using a route that includes a connection to a safe as an owner, we should give the user the option to manually define the safe tx nonce, rather than relying on the nonce provided by the safe tx service. This way users can override pending transactions that have not yet been signed/executed.