Release workflow - open a PR with changes instead of direct push

[sutaakar]

Issue link

Fixes #200

What changes have been made

Release workflow was altered to open a PR with code changes instead of pushing changes directly.

Verification steps

Can be verified using own fork of codeflare-operator repository.
Setup the required secrets for your fork:

• CODEFLARE_MACHINE_ACCOUNT_TOKEN - personal access token with rights to create PRs
• QUAY_ID, QUAY_TOKEN - credentials for Quay account to push images to
  Push changes in this PR into your repository fork on main branch.
  Manually run the workflow, provide workflow parameters pointing to your own repositories (to avoid messing with official repos).

You can see results on my fork:
https://github.com/sutaakar/codeflare-operator/actions/runs/5694084278
sutaakar#14

Checks

• I've made sure the tests are passing.
• Testing Strategy
  • Unit tests
  • Manual tests
  • Testing is not required for this change

[anishasthana]

/lgtm

[openshift-ci]

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