Implement go.mod viewer

What does this MR do?

Implements a blob viewer and dependency linker for go.mod files:

• Adds BlobViewer::GoMod < DependencyManager
• Adds GitLab::DependencyLinker::GoModLinker < BaseLinker
• Define types for go.mod and go.sum in GitLab::FileDetector
• Adds GoMod to Blob::AUXILIARY_VIEWERS and GoModLinker to Gitlab::DependencyLinker::LINKERS

Closes #212708 (closed)

• [go.mod, go.sum] " This project manages its dependencies using Go Modules. Learn more" will be shown under the commit info.
• [go.mod, go.sum] Packages hosted on the instance will link to the project
  • For example, on GitLab.com, module gitlab.com/gitlab-org/gitaly will link to https://gitlab.com/gitlab-org/gitaly
• [go.mod, go.sum] Packages not hosted on the instance will link to a specific version on pkg.go.dev
  • For example, on example.com, requires gitlab.com/rigel314/pakparse v0.1.0 will link to https://pkg.go.dev/gitlab.com/rigel314/pakparse@v0.1.0
• [go.sum] Checksums will link to sum.golang.org
  • For example, the checksum in gitlab.com/rigel314/pakparse v0.1.0 h1:rX1X0Woi0Cei2otdqlJNwVY3qdsKKHSvTWOR6jyh2jo= will link to https://sum.golang.org/lookup/gitlab.com/rigel314/pakparse@v0.1.0

Screenshots

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
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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