Release version 3.0.0

[github-actions]

Proposed changelog:

This release aggregates the the work previously done in separate repositories for AWS S3 Connector and GCS Connector. From now on this repository will contain both connectors as well as commons library. Old AWS S3 Connector and GCS Connector repositories are now archived.

What's changed:

Common changes

• Added metadata descriptor to enable Apache Kafka Connect use the plugin discovery mechanism build: add metadata descriptor to enable kafka connect use the plugin discovery mechanism #285
• Various dependency upgrades
• All Gradle scripts migrated to Kotlin

Aiven's S3 connector for Apache Kafka

• Added support for setting SSEA name Add Support for setting SSEA name s3-connector-for-apache-kafka#296
• Use default or custom provider chain for AWS S3 authentication Use default or custom provider chain for s3 authentication s3-connector-for-apache-kafka#355
• The produced release artifact is now renamed to s3-sink-connector-for-apache-kafka as well as produced jar
  file is renamed to s3-sink-connector-for-apache-kafka

Aiven's GCS connector for Apache Kafka

• Added support for automatic discovery of default credentials https://github.
  com/Add support for autodiscovering default credentials gcs-connector-for-apache-kafka#292
• Added support for setting object metadata Content-Encoding feat: Add support for setting object metadata Content-Encoding gcs-connector-for-apache-kafka#359
• The produced release artifact is now renamed to gcs-sink-connector-for-apache-kafka as well as produced jar
  file is renamed to gcs-sink-connector-for-apache-kafka

[eliax1996]

LGTM