Add Maven commands to package detail page

What does this MR do?

Adds Maven installation commands to the Maven package details page, similar to how they've recently been added for NPM packages.

Currently, the Setup tab is only displaying minor content. Further content will either be added as part of a follow up MR or this MR if the required backend work is small.

Screenshots

As of commit 2f0bb805828:

Installation	Setup

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #7603 (closed)