Update to gradle 7.3 (maintainer copy)

What does this MR do?

Updated gradle version from 6.7.1 to 7.3.3 (only 7.3.x support java 17) and fixed gradle-plugin build script according to documentation for migration to Gradle7.

This is the maintainer MR which is needed in order to run the QA bridge jobs (downstream pipelines using Secure test projects). Credit to @gliDom for contributing the original MR Add support for java 17.

Documentation

Documentation has been updated as part of Draft: Gradle 7.3 is added to Tested version created by @gliDom

What are the relevant issue numbers?

N/A

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer