Allow whitelisted IPs to bypass API rate limits

[rileyhgrant]

Related:

• issue: Consider increasing rate limit for specific university IPs #1710
• terraform PR for api gcs read permissions: https://github.com/broadinstitute/gnomad-terraform/pull/202

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Overall the strategy to have a list of whitelisted IPs thats private is:

• Store the IPs (and other details for readability) in a json file in GCS
• Give the API kubernetes service account access to read from GCS
• On API startup, load the IPs from the json file into memory
• On each api call, check the IP against the array of whitelisted IPs in memory
  • Skip the rate limiting if the IP is whitelisted

Curious as to a few things:

1. Does this approach seem reasonable?
2. Is completely bypassing rate limiting fine? Or should we just give a more lenient rate limit to whitelisted IPs