chore(psbt): clone uses correct fromBuffer

Enables extension of Psbt to support other chains

Ticket: BG-00000

Author: davidkaplanbitgo

src/psbt.js

@@ -152,7 +152,7 @@ class Psbt {
   }
   clone() {
     // TODO: more efficient cloning
-    const res = Psbt.fromBuffer(this.data.toBuffer());
+    const res = this.constructor.fromBuffer(this.data.toBuffer(), this.opts);
     res.opts = JSON.parse(JSON.stringify(this.opts));
     return res;
   }

ts_src/psbt.ts

@@ -216,7 +216,10 @@ export class Psbt {
 
   clone(): Psbt {
     // TODO: more efficient cloning
-    const res = Psbt.fromBuffer(this.data.toBuffer());
+    const res = (this.constructor as typeof Psbt).fromBuffer(
+      this.data.toBuffer(),
+      this.opts,
+    );
     res.opts = JSON.parse(JSON.stringify(this.opts));
     return res;
   }