Add flag for all frame initiators to finchtrial config.

We are planning to flip this behavior in the dogfood + launch studies to align with other browsers and unbreak certain 3PC flows.

Change-Id: I00fa42005a58c4a5a61c4daa56b330bdaf1d1a63
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5097943
Commit-Queue: Anton Maliev <amaliev@chromium.org>
Reviewed-by: Jonathan Njeunje <njeunje@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1234551}

testing/variations/fieldtrial_testing_config.json

@@ -18074,6 +18074,7 @@
                     "name": "Enabled",
                     "params": {
                         "TpcdBackfillPopupHeuristicsGrants": "30d",
+                        "TpcdPopupHeuristicEnableForIframeInitiator": "all",
                         "TpcdReadHeuristicsGrants": "true",
                         "TpcdRedirectHeuristicRequireABAFlow": "true",
                         "TpcdRedirectHeuristicRequireCurrentInteraction": "true",