docs: document RHDP wrapper deployment path and configurable secrets locations for coco-pattern

[butler54]

The coco-pattern getting-started guide (content/patterns/coco-pattern/coco-pattern-getting-started.adoc) and Azure requirements page (coco-pattern-azure-requirements.adoc) don't currently mention the rhdp/ wrapper scripts (rhdp/wrapper.sh, rhdp/wrapper-multicluster.sh, rhdp/wrapper-cluster-only.sh) at all, even though they're the recommended, opinionated Azure deployment path (see validatedpatterns/coco-pattern#59 comment thread: "inside the repo is a folder called rhdp. That (for our tech sellers) provides an opinionated path to complete deployment that is stable... That wrapper script is probably the best place to understand the deployment process").

As of validatedpatterns/coco-pattern#130, these wrapper scripts also support:

• Overriding the OpenShift pull secret location via PULL_SECRET (env var) or --pull-secret (CLI flag on rhdp/rhdp-cluster-define.py), instead of requiring ~/pull-secret.json.
• Overriding the SSH public key location via SSH_PUBLIC_KEY (env var) or --ssh-public-key, with auto-detection preferring ~/.ssh/id_ed25519.pub, then id_ecdsa.pub, then id_rsa.pub if no override is given (previously hardcoded to ~/.ssh/id_rsa).

Requesting:

1. A short pointer/section introducing the RHDP wrapper scripts as a supported, opinionated Azure deployment path (linking to rhdp/README.md in the repo for full details).
2. Documentation of the pull-secret/SSH-key override behavior and the new Ed25519-preferred default.

This is scoped narrowly to the above — see validatedpatterns/coco-pattern#120 for the broader documentation overhaul (bare-metal onboarding, mixed TEE types), which is a separate, larger effort.

[butler54]

Moving this to be tracked in the pattern repo instead: validatedpatterns/coco-pattern#131. Closing here to avoid duplicate tracking.