generator: consider converting repeated fields to HTTP query parameters

[scotthart]

Currently, we skip repeated fields found in proto request messages when formatting query parameters for GET requests. This may or may not be correct and needs some investigation.

[coryan]

Closing for now, does not seem to be needed.

[dbolduc]

If these fields are not included in the body, then they are not currently sent over the wire.

We have to include them as query parameters. Luckily, the google.api.http proto is well documented and tells us how to do it:

https://github.com/googleapis/googleapis/blob/a91d1a37cb86a0e49fdc21d8b4416eb1c2a083ec/google/api/http.proto#L116-L117