Export `<CI_CNT>` and `<B_CNT>` as RPM macros

[Conan-Kudo]

Is your feature request related to a problem? Please describe.
In Fedora Linux, we're working on adding support for build counters to our default packaging through a (future) buildsystem controlled macro called %buildrelease.

Describe the solution you'd like
I would like <CI_CNT> and <B_CNT> to be exported as macros in the RPM build environment.
Since these are OBS-specific, I think it would make sense to export them like so:

%_obs_commit_count <CI_CNT>
%_obs_build_count <B_CNT>

Then, Fedora OBS targets can be defined with:

Release: <SPEC_REL>

Macros:
%buildrelease ~obs%{_obs_commit_count}.%{_obs_build_count}
:Macros

Describe alternatives you've considered
The only real alternative I've considered is having OBS continue to ignore the feature and rewrite the Release: field as it does today. There aren't really any other options that would work with this approach.

Additional context
The details of the %buildrelease macro are discussed in pagureio#fesco#3501.