* This patch makes pages with the `OPENER_POLICY_SAME_ORIGIN_EMBEDDER_POLICY_REQUIRE_CORP` policy load into a special `webCOOP+COEP={pageOrigin}` remote type.
* Adds `E10SUtils.WEB_REMOTE_COOP_COEP_TYPE_PREFIX="webCOOP+COEP="`
* When a COOP process switch occurs and the target page doesn't have this policy, we pass a `preferredRemoteType="web"` into `E10SUtils.getRemoteTypeForPrincipal` ensuring that we correctly get a different `remoteType`
* E10SUtils.getRemoteTypeForPrincipal is changed such that `if preferredRemoteType.startsWith(WEB_REMOTE_COOP_COEP_TYPE_PREFIX)` we don't override it with `webIsolated={pageOrigin}`.
* `coop_header.sjs` is changed to also allow setting `Cross-Origin-Embedder-Policy` headers
* `browser_httpCrossOriginOpenerPolicy.js` is changed to test that pages are correctly opened in the correct remoteType process.
Differential Revision: https://phabricator.services.mozilla.com/D48715
06c9b1569f