Update AI Gateway middleware and interceptor to handle deployment_type header

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Problem

Currently, we do not have a clear way to identify deployment type. realm is very limited and is showing false value in many cases.

We need new field deployment_type that should help us distinguish this.

Solution

• #576215 issue will add new header in GitLab monolith x-gitlab-deployment-type

• Update schema version of billing and standard context. Add new field deployment_type in the context definition.

• Update code in middleware and interceptor to accept that value and pass it to standard context and billing context.