fix: use base repo for reference benchmarks and head_ref for tests

[antonbaliasnikov]

What ❔

• For forks, always use base repo for the reference testing in benchmarks
• Use head_ref in the base scenario for forks integration tests to not take main by default with workflow_call. This leads to issues when some other branch (not main) in forks repositories is used, and main is not rebased from the upstream repo.

Why ❔

We have to prevent a situation when a fork repository main branch is not rebased, but some other branch is.

Checklist

• PR title corresponds to the body of PR.
• Documentation comments have been added / updated.