`ElectrumResultExt` trait is also introduced that adds methods which can convert the `Anchor` type for the update `TxGraph`. We also make use of the new `TxCache` fields in `SyncRequest`/`FullScanRequest`. This way, we can avoid re-fetching full transactions from Electrum if not needed. Examples and tests are updated to use the new `ElectrumExt` API.