Prepare necessary changes for vitest 3.x

[Cherry]

Describe the solution

Vitest 3.x will be released in January, powered by Vite 6.

More details: vitest-dev/vitest#6992

The primary breaking change here will likely just need to be adding environments.ssr.resolve.conditions to the config defined at

workers-sdk/packages/vitest-pool-workers/src/config/index.ts

Line 140 in ff8f5ae

ensureArrayIncludes(config.resolve.conditions, requiredConditions);