* [release/7.0] Use simpler Docker tags
- `cherry-pick` of 5f4bc82d, Update docker tag to latest schema
  - This change moves all of the docker images to the -latest tag as part of #10377.
- `cherry-pick` of f79f2d1c, Replace -latest docker tags with new schema
  - We changed the latest tags to not include the -latest suffix, so this change updates those tags to the new schema.

nit: Correct timeout of source-build job
- not honoured as a top-level parameter to source-build.yml

* !fixup! Use rh-ruby26

Co-authored-by: Michelle McDaniel <michelm@microsoft.com>