fix: support setting STORAGE_EMULATOR_HOST without /storage/{version} suffix

[jack-michaud]

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Fixes #752 🦕

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This is a draft and an attempt to fix #752.

The python client makes a request for a blob using this format (which returns an HTTP 404)

http://localhost:9199/storage/v1/b/redacted-bucket.appspot.com/o/user-uploads%2F4f721203-0103-408c-96aa-526d8e2ac2b1%2Fpublic%2Foriginal%2Fsignal-2021-10-19-122916.jpeg?projection=noAcl&prettyPrint=false

Compared to the NodeJS's implementation, which requests

http://localhost:9199/b/redacted-bucket.appspot.com/o/user-uploads%2F4f721203-0103-408c-96aa-526d8e2ac2b1%2Fpublic%2Foriginal%2Fsignal-2021-10-19-122916.jpeg

The notable difference is that there's no /storage/v1/ prefix. This is similar to the issue called out in firebase/firebase-tools#3508 (comment).

Changing the base URL to a URL which the emulator can handle by following the NodeJS implementation of the STORAGE_EMULATOR_HOST environment variable is my attempt to fix the issue.

It seems to work for getting file blobs, but does not currently work with Uploads (using the test example from #752).

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[jack-michaud]

After further investigation, this PR doesn't fix the issue linked. This still provides a fix for a different issue. I'll make an issue tomorrow to confirm that this approach is reasonable.

[eliasposen-ivy]

Hey @jack-michaud ! I'm running into this same issue with the latest released package. I don't see your fix in main, was a new issue created to track/resolve this?

Thanks