Update the release steps for "Cherry Pick Commits" and "Update Version in Code"

[ptodev]

Fixing a few issues with the release docs:

• The example PRs used to point to the Agent.
• It wasn't very clear what the VERSION file should point to.
• There is a "Test Release" step which is a bit ambiguios. I think we should remove it and replace it with a CI check.
• Combining the "Cherry Pick Commits" and "Update Version in Code" steps into one

I find it confusing to have "Cherry Pick Commits" and "Update Version in Code" as two separate steps. It's more efficient (and less confusing) to explain those things in the same step. It also makes the instructions less verbose.