feat(babylonlabs-io-btc-staking-ts): change createBtcDelegationMsg method to public

Make the createBtcDelegationMsg method public to allow access from outside
the BabylonBtcStakingManager class.

Issue: BTC-2143

Co-authored-by: llm-git <[email protected]>

Author: OttoAllmendinger

modules/babylonlabs-io-btc-staking-ts/src/staking/manager.ts

@@ -801,7 +801,7 @@ export class BabylonBtcStakingManager {
    * @param inclusionProof - The inclusion proof of the staking transaction.
    * @returns The protobuf message.
    */
-  private async createBtcDelegationMsg(
+  public async createBtcDelegationMsg(
     channel: "delegation:create" | "delegation:register",
     stakingInstance: Staking,
     stakingInput: StakingInputs,