min-base-fee: conduct Failure Modes Analysis

[geoknee]

Alternative risk modelling is totally acceptable, please check in with @mds1 about the latest advice.

See #295 and implementation work can be discovered through the parent tracking ticket.

Specific TODOs

• Check how a state growth figure was obtained for the operator fee, and do the same for MinBaseFee
• Check the operator fee FMA for any other mitigations which may apply to MinBaseFee

[mslipper]

This is complete, see https://www.notion.so/oplabs/MinBaseFee-Threat-Model-241f153ee162807dbc0ff1f598059a46.