Add collections and instances (#5)

.github/workflows/cron-test.yaml

.github/workflows/test.yml

CHANGELOG.md

docs/data-sources/collection.md

docs/data-sources/collection_instance.md

docs/resources/collection.md

docs/resources/collection_instance.md

e2e/authority.tf

e2e/ca.crt

e2e/managed.tf

e2e/provider.tf

e2e/provisioner.tf

examples/data-sources/smallstep_collection/data-source.tf

...data-sources/smallstep_collection_instance/data-source.tf

examples/resources/smallstep_collection/import.sh

examples/resources/smallstep_collection/resource.tf

examples/resources/smallstep_collection_instance/import.sh

examples/resources/smallstep_collection_instance/resource.tf

internal/apiclient/v20230301/api.gen.go

internal/apiserver/v20230301/api.gen.go