Revamp deployer decision model page to include or link to CISA BOD 26-04 model #1174

Is your feature request related to a problem? Please describe.

With the addition of #1164, we now have two "deployer decision models":

1. https://certcc.github.io/SSVC/howto/deployer_tree/
2. https://certcc.github.io/SSVC/howto/cisa_response/

Describe the solution you'd like

Keep both models, but unify the content so that they refer to each other or provide some guidance on when to use one versus the other.

Describe alternatives you've considered

Doing nothing leaves us with two pages that describe different decision models for deployers while lacking clarity on "when should I use A vs B?"