settings: figure out how are we doing settings now

[lgadban]

#10458 removes the existing usage of Settings and replaces it with a simple environment variable based solution.

We need to decide the long-term solution for global settings config:

• is it captured in a CRD?
• does it dynamically reload the control plane on change?
• is it actually needed?

Additionally, for the current env var solution, the current flags (as of the linked PR) do not need to be global now that we have truly per-Gateway translation. These flags can be theoretically moved to e.g. GatewayParams so we should analyze that feasibility.