lint/noNamespace could ignore ambient namespaces

[Conaclos]

Currently, the noNamespace reports any namespaces.

The equivalent ESLint rule no-namespace provides two options allowDeclarations (default is false) and allowDefinitionFiles (default is trtue). allowDeclarations allows namespace in ambient contexts (declare namesapce, namespace inside declare global {} and declare module "mod" {}). allowDefinitionFiles allows namespaces in declaration files (.d.ts). Most of the users seem to use the default configuration.

I propose to change the behavior of our rule to allow ambient namespaces, including namespaces in declaration files.
This is technically a breaking change. We could make this change in Biome 2.0. With this change, we should allow more use cases of namespaces, which might allow us to make the rule recommendable.