doc: improve release documentation

Extract the "Cherry-pick the Release Commit to master" part to its own
section and be more precise about what should be done to handle
conflicts.

PR-URL: https://github.com/nodejs/node/pull/33042


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Beth Griggs <Bethany.Griggs@uk.ibm.com>