feat(cheats): add `writeFork..` cheats to write vars into `fork.<chain>` of `foundry.toml`

[0xrusowsky]

Component

Forge

Describe the feature you would like

ref:

• Native Multichain Scripting Workflow #11078

as a follow-up, of the already created readFork.. cheats, we should also add the ability to set variables to inform about deployments, etc.

Additional context

No response