feat(babylonlabs-io-btc-staking-ts): change private fields to protected

Change class fields from private to protected to enable proper inheritance
in BabylonBtcStakingManager.

Issue: BTC-2143

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

Author: OttoAllmendinger

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

@@ -40,11 +40,11 @@ import { createCovenantWitness } from "./transactions";
 
 export class BabylonBtcStakingManager {
   constructor(
-    private network: networks.Network,
-    private stakingParams: VersionedStakingParams[],
-    private btcProvider: BtcProvider,
-    private babylonProvider: BabylonProvider,
-    private ee?: Emitter<ManagerEvents>,
+    protected network: networks.Network,
+    protected stakingParams: VersionedStakingParams[],
+    protected btcProvider: BtcProvider,
+    protected babylonProvider: BabylonProvider,
+    protected ee?: Emitter<ManagerEvents>
   ) {
     this.network = network;