Delegate batch proving

Batch proving now actually includes non-trivial amount of computation (https://github.com/0xMiden/protocol/pull/3859#discussion_r3999656928).

This means we should offload batch proving from locally on the sequencer, to a beefy remote prover.

The remote proving service may not be available in time - make the remote url optional so that batch proving can be skipped altogether if unspecified.

Don't forget to add a batch proving service to the local dev network compose setup, in the same optional fashion as the transaction prover.

Start by searching the node codebase for batch proving in the sequencer and for the existing optional transaction prover configuration. Compare that with the local dev network compose setup mentioned in the issue. Done means batch proving uses a remote prover when a URL is configured, is skipped when unspecified, and the compose setup has an optional batch proving service.

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