Documentation for post rc.0 cut tasks

[mbianchidev]

After the 1.33.0-rc.0 cut, we realized we need to better document the whole process to follow after any rc.0 cut:

These is a rough list of the tasks/pulls required:

1. https://github.com/kubernetes/test-infra/pull/34650/files
2. https://github.com/kubernetes/test-infra/pull/34651/files
3. Most stuff is done by this PR from Jim https://github.com/kubernetes/test-infra/pull/34668/files (cmake command)
   3.1 read and write about this Slack thread for detailed steps for this: (note: most stuff is autogenerated by the cmake command)
4. ./hack/run-in-python-container.sh ./releng/generate_tests.py --yaml-config-path ./releng/test_config.yaml (see this PR)
5. Publishing bot staging/publishing: add release-1.33 rules kubernetes#131250
6. Look at this DM from Jim with some more info on the CLI side of things
7. Perf branch Need 1.33 branch? perf-tests#3290 (comment)

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6. Remove 1.29 jobs drop 1.29 from image variants, 1.29 is EOL test-infra#34674 (version to be removed or not varies depending on where in the overall release cycle we are in terms of EOL support) - this could actually be step 0, first drop old jobs and then add new ones so the prow cluster is never overwhelmed - but it could be actually a patch release job that has to be performed instead of doing it before/during rc.1 (see Slack convo with @BenTheElder )

Extra: fix line 307 of this script to avoid having a "release job" message for nomock stage commands being run (could cause random panic) and generally error messages could use some more polish

For context see: #2755