Add github workflow running jenkins job

[sylwiaszunejko]

This workflow pushes scylla-bench docker image using gocql version from the PR and triggers jenkins job that uses this image of scylla-bench.

[sylwiaszunejko]

New workflow won't be running in CI in this PR, because it uses pull_request_target event. In this PR we can see how it behaves: #255.

Things to be changed:

• change jenkins_client fork to scylladb
• change user from me to some official jenkins user
• move jenkins job to official location

To check if the authorize part work correctly for the PRs from external users (forks) we would need to merge this PR and than check. That isn't perfect solution but right now I can't see other way.

[dkropachev]

Let's move this logic to scylla-bench repo.
So that here it would look like:

      - name: Build and push scylla-bench image
        run: |
           cd scylla-bench
           GOCQL_COMMIT_ID="${{ github.event.pull_request.head.ref }}" IMAGE_TAG="scylladb/gocql-extended-ci:scylla-bench-${NAME}" make build-image-with-custom-gocql-commit
           docker push "scylladb/gocql-extended-ci:scylla-bench-${NAME}"

[sylwiaszunejko]

scylladb/scylla-bench#143

[dkropachev]

Isn't it default ? can't you just use path: gocql ?

[sylwiaszunejko]

it seems to be not, look: https://github.com/scylladb/gocql/pull/255/checks
Or do you mean I should add path: gocql in some other place?

[sylwiaszunejko]

I went with @Lorak-mmk advice #204 (comment)
Now the changes are here: #255 and here we can see the new workflow running: #263
Please move to these two PR with all discussions