feat: defineEnv util

[pi0]

This PR adds a new defineEnv({ presets: [], ... }): { env } utility aiming to replace env(presets[]): env util for integration usage.

The benefit of this one is that it can be extendable with more features, options and shortcuts.

Example:

const { env } = defineEnv({
 nodeCompat: true,
 presets: [myPreset],
 overrides: {}
});

[pi0]

(merging as experimental to iterate and improve API features)