Rename RPC endpoint `PublishAndLogTransfer`

[ffranr]

The PublishAndLogTransfer RPC accepts a fully signed, anchored asset transfer and inserts it into the ChainPorter state machine. The state machine may then broadcast the anchor transaction, wait for confirmation, handle transfer proofs, and persist state to the DB.

The current name focuses on low-level actions (“publish” and “log”) which are imprecise and not fully representative of the RPC's role. A more descriptive name like ExecPreAnchoredTransfer better communicates the higher-level intent: executing a transfer that is already anchored and ready for processing. With a higher level name, optional flag args to skip broadcast make more sense.

Tasks:

• Rename PublishAndLogTransfer to ExecPreAnchoredTransfer, including any test or helper methods.
• Mark PublishAndLogTransfer as deprecated in the proto definition and update its docstring:

    /*
    PublishAndLogTransfer is deprecated and will be removed after v0.7.
    Use `ExecPreAnchoredTransfer` instead.

    This endpoint accepts a fully committed and signed anchor
    transaction and publishes it to the Bitcoin network. It also logs the
    transfer of the given active and passive assets in the database and ships
    any outgoing proofs to the counterparties.
    */
    rpc PublishAndLogTransfer (PublishAndLogRequest)
        returns (taprpc.SendAssetResponse) {
        option deprecated = true;
    }