Generate library for google/monitoring/metricsscope/v1

[coryan]

This is blocked by:

• Missing LRO mixin in some APIs #781

---

Generate with:

cargo new --lib --vcs none src/generated/monitoring/metricsscope/v1
taplo fmt Cargo.toml 
go -C generator/ run ./cmd/sidekick generate     -project-root ..     -specification-source google/monitoring/metricsscope/v1     -service-config google/monitoring/metricsscope/v1/monitoring.yaml -output src/generated/monitoring/metricsscope/v1
cargo fmt

The build fails:

typos && cargo fmt && cargo clippy -- --deny warnings && cargo test && cargo doc
error[E0433]: failed to resolve: use of undeclared type `GetOperation`
   --> src/generated/monitoring/metricsscope/v1/src/builders.rs:187:30
    |
187 |                     let op = GetOperation::new(stub)
    |                              ^^^^^^^^^^^^ use of undeclared type `GetOperation`
    |
help: a type alias with a similar name exists
    |
187 |                     let op = Operation::new(stub)
    |                              ~~~~~~~~~
help: consider importing this struct
    |
18  +     use longrunning::builders::operations::GetOperation;
    |

I think because the YAML file does not even list GetOperation in the HTTP rules overrides:

https://github.com/googleapis/googleapis/blob/master/google/monitoring/metricsscope/v1/monitoring.yaml

Unlike the prior cases (Bigtable and Cloud Build), where they do:

http:
  rules:
  - selector: google.longrunning.Operations.CancelOperation
    post: '/v2/{name=operations/**}:cancel'
  - selector: google.longrunning.Operations.DeleteOperation
    delete: '/v2/{name=operations/**}'
  - selector: google.longrunning.Operations.GetOperation
    get: '/v2/{name=operations/**}'
  - selector: google.longrunning.Operations.ListOperations
    get: '/v2/{name=operations/projects/**}/operations'

https://github.com/googleapis/googleapis/blob/47444ff0e3c8bca6c74ee0e8412aa747a9e0126d/google/bigtable/admin/v2/bigtableadmin_v2.yaml#L45-L54