feat(fixtures): Hardfork Execution Test Fixtures

[refcell]

Description

With the opt8n tool successfully generating execution test fixtures in the fixtures/execution/ directory, the next step is to generate a bunch of test fixtures and document the process along the way.

This ticket is to generate execution test fixtures surrounding the various network upgrades aka hardforks. To properly test hardfork execution behavior, we need test fixtures that assert correct behavior both prior to the hardfork and after it's enabled.

Hardforks (listed in specs.optimism.io)

• Regolith
• Canyon
• Delta
• Ecotone
• Fjord

[ewoolsey]

Currently blocked by https://github.com/foundry-rs/foundry/pull/8749

Will come back to this when that's merged in.