Use base64.URLEncoding for []byte parameters in query

[tvoll]

Changes encoding method to base64.URLEncoding for query parameters of type []byte.

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[johanbrandhorst]

Hi, please rebase on master, we've changed our generation strategy quite a bit with #1971.

[johanbrandhorst]

Hi, this change looks great to me, thanks for your contribution. Can you please sign the CLA?

[tvoll]

@googlebot I signed it!

[johanbrandhorst]

Thanks for your contribution!

[tvoll]

@johanbrandhorst Thank you for all of your work! I'm still blown away by what you can achieve with gRPC transcoding.