Use .tar.gz instead of Git refs for NGINX source modules

What does this MR do?

If the Omnibus build cache were present, previously the ngx_security_headers and nginx-module-vts components would often be built with master instead of tagged versions. This happened because Omnibus' GitFetcher clones the repositories and only checks out the specific version when building the component. The nginx component assumes that the Omnibus source directory has the right version, but if nothing changed with ngx_security_headers and nginx-module-vts then the git checkout will not occur.

To avoid this trouble with GitFetcher, we need to do two things:

1. Download the source .tar.gz directly. This preserves the version manifest and license information.

2. Extract these .tar.gz inside the NGINX software definition itself. Because the ngx_security_headers and nginx-module-vts components don't change /opt/gitlab, the Omnibus build cache will generally assume that it doesn't need to extract the source code.

Related issues

Relates to #9066 (closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• MR title and description are up to date, accurate, and descriptive.
• MR targeting the appropriate branch.
• Latest Merge Result pipeline is green.
• When ready for review, MR is labeled workflowready for review per the Distribution MR workflow.

For GitLab team members

If you don't have access to this, the reviewer should trigger these jobs for you during the review process.

• The manual Trigger:ee-package jobs have a green pipeline running against latest commit.
• If config/software or config/patches directories are changed, make sure the build-package-on-all-os job within the Trigger:ee-package downstream pipeline succeeded.
• If you are changing anything SSL related, then the Trigger:package:fips manual job within the Trigger:ee-package downstream pipeline must succeed.
• If CI configuration is changed, the branch must be pushed to dev.gitlab.org to confirm regular branch builds aren't broken.

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes.
• Documentation created/updated.
• Tests added.
• Integration tests added to GitLab QA.
• Equivalent MR/issue for the GitLab Chart opened.
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.