Add e2e tests for IP Whitelist

[diazjf]

Adds e2e test for the whitelist-source-range annotation.
Part of the #3124 effort.

[ElvinEfendi]

@diazjf thanks for all these e2e tests.

Can you default to treating the Nginx together with its generated configuration as a black box an assert on response headers/body? As a user I don't care how Nginx does it as long as it does what I want. In this specific PR (EDIT: this is actually about another PR #3302) for example, you can assert those specific headers you set using custom server snippet are actually included in response headers.

But I acknowledge that sometimes it's just good enough to assert generated configuration.

[aledbf]

@diazjf please rebase to fix the e2e issue

[diazjf]

/assign @aledbf

[aledbf]

/lgtm
/approve

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