We need to add support for dynamic sidetags in CentOS Stream koji which mirrors the setup of the RHEL internal sidetag.

The RHEL setup is described in https://docs.engineering.redhat.com/display/EXDSPRHELB/Brew+side+tag+definitions

Most importantly we use the following agreement on the sidetag naming:

for gated sidetags we use template

rhel-{version}-{sidetag_id}-stack-gate

For example in rhel-8.4.0-z-dnf-stack-gate the version is 8.4.0-z, the sidetag_id is dnf.

For dynamic sidetags sidetag_id is a number:

rhel-8.4.0-z-1234565-stack-gate

We need the CentOS Stream also to follow this schema, so that we can configure sync process based on the regexp applied to the tag name.

Suggested template for centos stream:

c9s-build-{sidetag_id}-stack-gate

For example c9s-build-12345-stack-gate