The @fuchsia_infra_examples module

This is a Bazel module exercising the API surface of @fuchsia_infra.

The @fuchsia_infra_examples//:infra target is continuously validated by the infra-bazel-rules builder in CQ and CI.

Keeping this as a separate module (rather than in the same module as @fuchsia_infra) helps better emulate the project structure of customers of @fuchsia_infra (especially around workspace setup), which is idiomatic for production-grade BCR modules. It also simplifies dependency management for dependencies that are used exclusively for testing (eg: @fuchsia_sdk).