Add Redis interceptor tracing

What does this MR do?

Add cache tracing and Redis tracing

This change adds Distributed Tracing support for two new types of events

1. Redis Calls
2. ActiveSupport (Rails) Caching Operations

The intention is to help application developers and infrastructure SREs to understand the pressure that caching operations can have on the application when running at scale.

The Redis and Caching spans can be viewed in the Jaeger UI by clicking the "Trace" link in the performance bar when running on GDK.

See

• https://gitlab.com/gitlab-org/labkit-ruby/merge_requests/12
• https://gitlab.com/gitlab-org/labkit-ruby/merge_requests/13
• https://gitlab.com/gitlab-org/labkit-ruby/merge_requests/16
• https://gitlab.com/gitlab-org/labkit-ruby/merge_requests/17

This change adds Redis tracing and ActiveSupport cache tracing to the application.

EE companion is https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/15545

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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