mobile: better api for java users (#21580)

* (mobile): Adds string representations for types

* mobile: better interfaces add stringer to types

Co-authored-by: sarath <sarath@melvault.com>

mobile/common.go

@@ -87,6 +87,11 @@ func (h *Hash) GetHex() string {
 	return h.hash.Hex()
 }
 
+// String implements Stringer interface for printable representation of the hash.
+func (h *Hash) String() string {
+	return h.GetHex()
+}
+
 // Hashes represents a slice of hashes.
 type Hashes struct{ hashes []common.Hash }
 
@@ -188,6 +193,11 @@ func (a *Address) GetHex() string {
 	return a.address.Hex()
 }
 
+// String returns a printable representation of the address.
+func (a *Address) String() string {
+	return a.GetHex()
+}
+
 // Addresses represents a slice of addresses.
 type Addresses struct{ addresses []common.Address }