[#4] New pipeline ensures that files shared by YDB and YDBEncrypt repos are updated in both repos

This commit adds a new checkforupdates pipeline which checks the following:

• Firstly, it checks that none of the files deleted from the YDB repo when YDBEncrypt was moved to its own repo have been recreated. If any of those files exist in YDB, the pipeline will fail.
• Secondly, it checks that the files shared by both the YDB and YDBEncrypt repos are in sync. If they are out of sync and the files haven't been changed in the current MR, the pipeline will fail. The check to make sure the files aren't changed in the current MR is to avoid pipeline failures for pending MRs on the YDBEncrypt side that make changes to these files. Once these MRs are merged, there will be a pipeline failure unless corresponding changes are made and merged in the YDB repo.

The purpose of this pipeline is so that it can be run nightly to ensure that the YDB and YDBEncrypt repos are kept in sync.