fix: Detect Pomerium proxy (#3219)

* chore: Remove unused DocumentList component

* fix: Add support for detecting Pomerium

* Refactor to avoid reading cookies on every request

* refactor: Just enable cookies for all self-hosted builds

* Remove unused userAgent

* test: Add window.env to mock

__mocks__/window.js

@@ -1 +1,2 @@
-window.matchMedia = data => data;
+window.matchMedia = (data) => data;
+window.env = {};