[sdk/javascript] Metadata - provide util to calculate delta (xor) value and delta length about symbol

[gimre-xymcity]

@Jaguar0625 can we close this one and #298 ?

[gimre-xymcity]

part of js sdk 3.0.4

[cryptoBeliever]

Works correctly. I'm able to calculate xor using util ✔️ :

    const textEncoder = new TextEncoder();
    const old_value = textEncoder.encode('some value')
    const new_value = textEncoder.encode('some new value')
    const value_delta = symbolSDK.symbol.metadataUpdateValue(old_value, new_value)

    const metadata = facade.transactionFactory.createEmbedded({
        type: 'account_metadata_transaction_v1',
        signerPublicKey: keyPair.publicKey,
        targetAddress: facade.network.publicKeyToAddress(keyPair.publicKey),
        scopedMetadataKey: 4n,
        value: value_delta,
        valueSizeDelta: new_value.length - old_value.length
    })

    const embedded_transactions = [metadata]
    const merkleHash = SymbolFacade.hashEmbeddedTransactions(embedded_transactions)

    const aggregateTransaction = facade.transactionFactory.create({
        type: 'aggregate_complete_transaction_v2',
        signerPublicKey: keyPair.publicKey,
        fee: 100000n,
        deadline: BigInt(timestamp + 3600n * 1000n), // 3600sec * 1000ms
        transactionsHash: merkleHash,
        transactions: embedded_transactions
    })