AG-19871 add probe nodes to the weakset

Merge in ADGUARD-FILTERS/tsurlfilter from fix/AG-19871 to master

Squashed commit of the following:

commit 9f20999
Author: Maxim Topciu <mtopciu@adguard.com>
Date:   Mon Feb 20 18:53:21 2023 +0200

    AG-19871 add probe nodes to the weakset

packages/tsurlfilter/src/content-script/css-hits-counter.ts

@@ -265,6 +265,11 @@ class CssHitsCounter {
             this.observer.disconnect();
         }
 
+        /**
+         * To avoid cases where two css hits counters try to append and remove the
+         * same elements one after the other, we do not append already met nodes.
+         */
+        const probesWeakSet = new WeakSet();
         let timeoutId: number | null = null;
         this.observer = new MutationObserver(((mutationRecords) => {
             // Collect probe elements, count them, then remove from their targets
@@ -285,11 +290,20 @@ class CssHitsCounter {
 
                     const { target } = mutationRecord;
                     if (!node.parentNode && target) {
+                        // If this node has been appended to the DOM and counted once, do not add
+                        // it again.
+                        if (probesWeakSet.has(node)) {
+                            return;
+                        }
                         // Most likely this is a "probe" element that was added and then
                         // immediately removed from DOM.
                         // We re-add it and check if any rule matched it
                         probeElements.push(node);
 
+                        // To ensure that this "probe" node has only been added once to the DOM,
+                        // we add it to the weak set.
+                        probesWeakSet.add(node);
+
                         // CSS rules could be applied to the nodes inside probe element
                         // that's why we get all child elements of added node
                         ElementUtils.appendChildren(node, childrenOfProbeElements);