feat request: namespace scoped EnvironmentConfig

### What problem are you facing?

After the change to namespace scoped composites and compositions i v2, it is no longer possible to create an EnvironmentConfig in a (namespaced) composition.

Indirectly creating a cluster scoped EnvironmentConfig, using an Object from provider-kubernetes, is painfull and goes against the move to namespace scoped resources.

### Usecase

One usecase (mentioned on [slack](https://crossplane.slack.com/archives/C08BBMDCH7W/p1769438184689339)) is sharing values between composites, where one composition creates an EnvironmentConfig which the other one imports into its environment. This way, an `id` can be transferred from the `status.atProvider` of one managed resource to the `spec.forProvider` of another managed resource in a different composition.

An alternative is to expose the values in the status of the composite, and use function-extra-resources or required resources to read it in the other composition. However, this results in the end-user seeing what might be confusing internal details in the status of their composites.

### How could this Function help solve your problem?

A namespace scoped EnvironmentConfig CRD could be created (either by Crossplane or the user), which this function would support loading into a composition environment. If created by Crossplane, `EnvironmentConfigs.apiextensions.crossplane.io` is already taken, and another apiGroup or kind would be needed.

The function would need to select between cluster and namespaced scoped EnvironmentConfig (default to cluster scoped), which could be a user defined apiVersion/kind selector as in [function-extra-resources](https://github.com/crossplane-contrib/function-extra-resources/blob/b37f7541731d7d035137a3ae021fd83439261850/input/v1beta1/resource_select.go#L112-L116), or a hardcoded apiVersion/kind if the CRD is created/provided by Crossplane.

The function could support reading namespace scoped EnvironmentConfigs from any namespace, but should default to the same namespace as the composite resource is within.