Add ability to prevent propagating experiment ids from WWW

Summary:
This diff adds the ability to prevent propagating experiment IDs from async jobs in WWW to Thrift services, and also adds gates to the methods that  set & add experiment ids.

I had already created the `lumos/experimentation:disable_www_exp_id_propagation` knob before I moved that logic from makeV to the specific call site in `FalcoFabricAsyncWriter`.

These calls are temporary to understand whether anything is calling add/set at all. If there is logic that is somehow adding/setting experiment ids, the JK UI will display the # of hits and we'll log a warning with the ids (and get a stacktrace). If it never gets hit (ie. nothing is calling add/set experiment ids), the JK UI will show no hits, and we will know for certain that the ids are being ingested via headers.

I also added a JK to control the rate at which we will log these api violations: `lumos/experimentation:www_experiment_id_api_violation_sampling_rate`. This is a safeguard in case we're somehow calling set/add experiment ids a lot, in which case we can log less by tweaking this rate.

Differential Revision: D70640520

fbshipit-source-id: daf2b61fbad166b392482e37cf09f725b93d8918

third-party/thrift/src/thrift/lib/hack/src/ThriftContextPropState.php

@@ -446,6 +446,10 @@ public static function getOriginIdResolver()[]: (function()[leak_safe]: int) {
       MCPProductID::UNKNOWN;
   }
 
+  public function clearExperimentIds()[write_props]: void {
+    $this->storage->experiment_ids = null;
+  }
+
   public function getExperimentIds()[]: vec<int> {
     $ret = $this->storage->experiment_ids;
     if ($ret !== null) {
@@ -454,18 +458,42 @@ public function getExperimentIds()[]: vec<int> {
     return vec[];
   }
 
-  public function addExperimentId(int $eid)[write_props]: void {
+  public function addExperimentId(int $eid)[zoned_shallow]: void {
+    if (!static::isExperimentIdModificationAllowed()) {
+      return;
+    }
     $v = $this->getExperimentIds();
     $v[] = $eid;
     $this->storage->experiment_ids = $v;
     $this->dirty();
   }
 
-  public function setExperimentIds(vec<int> $eids)[write_props]: void {
+  public function setExperimentIds(vec<int> $eids)[zoned_shallow]: void {
+    if (!static::isExperimentIdModificationAllowed()) {
+      return;
+    }
     $this->storage->experiment_ids = $eids;
     $this->dirty();
   }
 
+  private static function isExperimentIdModificationAllowed(
+  )[zoned_shallow]: bool {
+    if (
+      !JustKnobs::eval('lumos/experimentation:enable_www_experiment_id_api')
+    ) {
+      $sampling_rate = JustKnobs::getInt(
+        'lumos/experimentation:www_experiment_id_api_violation_sampling_rate',
+      );
+      if (coinflip($sampling_rate)) {
+        FBLogger('lumos_experimentation', 'disallowed experiment id call')
+          ->setBlameOwner('lumos')
+          ->warn('Experiment ID modifications are disallowed!');
+      }
+      return false;
+    }
+    return true;
+  }
+
   /**
    * This should not be exposed publicly, and instead call
    * getPrivacyUniverseDesignator