Allow Customization of port, host, and scheme in presigned Functions for Enhanced Security

[mskayali]

The presigned functions in the following file:
https://github.com/xtyxtyx/minio-dart/blob/3a59a0d277a69719d98108ce6ddae2ec82f8b320/lib/src/minio_sign.dart

Currently, these functions rely on URL information defined in the Minio client. However, when generating presigned URLs, the server URL is used for signing. Due to security concerns, the server URL may differ for internal (intra-network) and external (internet-facing) networks.

To address this, it is necessary to allow optional customization of the port, host, and scheme parameters when generating presigned URLs. This enhancement would provide greater flexibility and address potential security concerns when using different network configurations.