[COOP report] Add support for report-only

This adds the support for report-only COOP triggered Browsing context
group switches.
During navigation, besides computing whether COOP triggers a BCG switch,
this also computes if any of the report-only policies would also trigger
a switch if they were effective, the resulting values are stored in
booleans within |CrossOriginOpenerPolicyStatus|.
This booleans are then used to trigger the navigation reports, and in a
follow up to trigger access reports.

Explainer [WIP]:
https://github.com/camillelamy/explainers/blob/master/coop_reporting.md

Specification [WIP]:
whatwg/html#5518

Bug: 1099208
Change-Id: I2cb66ec5cdcd9d5b4658c28f0608bc6b52d0da6b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2241529
Commit-Queue: Pâris Meuleman <[email protected]>
Reviewed-by: Camille Lamy <[email protected]>
Reviewed-by: Arthur Hemery <[email protected]>
Auto-Submit: Pâris Meuleman <[email protected]>
Cr-Commit-Position: refs/heads/master@{#790781}

html/cross-origin-opener-policy/reporting/navigation-reporting/reporting-popup-same-origin-coep-report-to.https.html

@@ -111,7 +111,7 @@
     SAME_ORIGIN,
     "",
     "",
-    `same-origin; report-to="${popupReportEndpoint.name}"`,
+    `same-origin; report-to="${popupReportOnlyEndpoint.name}"`,
     "require-corp",
     [
       {
@@ -127,7 +127,8 @@
           "url": `${location.href}`,
           "type": "coop"
         }
-      },]
+      }
+    ]
   ],
   // Open a cross-origin popup with a same-origin COOP report only. A report is
   // sent to both this page's endpoint and the popup's.