fix: narrow generated API types

[briangregoryholmes]

The lack of required properties in the Swagger yaml results in the generated types to have unnecessary optional properties, which results in avoidable conditional checks on the applications side. This PR fixes that issue on the "supply side" for a few of the most impactful properties, but does not remove the conditional checks.

[begelundmuller]

Unfortunately, I think these annotations will just be overridden next time we run make proto.generate. For the change to persist, I think it would require a config change in proto/buf.gen.openapi-runtime.yaml or one of its adjacent files, but I'm not sure if it's possible.

[briangregoryholmes]

Looks like there are annotations we can add to the proto files as seen here: (https://grpc-ecosystem.github.io/grpc-gateway/docs/mapping/customizing_openapi_output/). Updated the PR.

[briangregoryholmes]

One small issue I'm running into:

Is it possible to change the type of the dimension_value field in MetricsViewComparisonRow to a string instead of the broader google.protobuf.Value? Changing it resulted in some type errors via the checks, but I'm not sure how or why this would be returned as anything other than a string. Want to hold off on fixing the errors if there's a reason I'm missing for using the other type.

Relatedly, this MetricsViewComparisonRow type (and related query) is being used to populate the list of possible dimension values when adding a filter, though it doesn't seem to be designed for that considering it's also pulling in measure data. Is there a better way to just get a plain list of these values (max 100) filtered by a search parameter?