Add a ListLinkHandler which can be used to be returned from ChannelInfo.getTabs() when a specific tab's data has already been fetched

This new ListLinkHandler, ReadyChannelTabListLinkHandler, should help saving
clients data, energy and time by helping to reduce duplicate requests.

Co-authored-by: Stypox <stypox@pm.me>

extractor/src/main/java/org/schabi/newpipe/extractor/linkhandler/ReadyChannelTabListLinkHandler.java

@@ -0,0 +1,55 @@
+package org.schabi.newpipe.extractor.linkhandler;
+
+import org.schabi.newpipe.extractor.StreamingService;
+import org.schabi.newpipe.extractor.channel.tabs.ChannelTabExtractor;
+
+import javax.annotation.Nonnull;
+import java.io.Serializable;
+import java.util.List;
+
+/**
+ * A {@link ListLinkHandler} which can be used to be returned from {@link
+ * org.schabi.newpipe.extractor.channel.ChannelInfo#getTabs() ChannelInfo#getTabs()} when a
+ * specific tab's data has already been fetched.
+ *
+ * <p>
+ * This class allows passing a builder for a {@link ChannelTabExtractor} that can hold references
+ * to variables.
+ * </p>
+ *
+ * <p>
+ * Note: a service that wishes to use this class in one of its {@link
+ * org.schabi.newpipe.extractor.channel.ChannelExtractor ChannelExtractor}s must also add the
+ * following snippet of code in the service's
+ * {@link StreamingService#getChannelTabExtractor(ListLinkHandler)}:
+ * <pre>
+ * if (linkHandler instanceof ReadyChannelTabListLinkHandler) {
+ *     return ((ReadyChannelTabListLinkHandler) linkHandler).getChannelTabExtractor(this);
+ * }
+ * </pre>
+ * </p>
+ */
+public class ReadyChannelTabListLinkHandler extends ListLinkHandler {
+
+    public interface ChannelTabExtractorBuilder extends Serializable {
+        @Nonnull
+        ChannelTabExtractor build(@Nonnull StreamingService service,
+                                  @Nonnull ListLinkHandler linkHandler);
+    }
+
+    private final ChannelTabExtractorBuilder extractorBuilder;
+
+    public ReadyChannelTabListLinkHandler(
+            final String url,
+            final String channelId,
+            @Nonnull final String channelTab,
+            @Nonnull final ChannelTabExtractorBuilder extractorBuilder) {
+        super(url, url, channelId, List.of(channelTab), "");
+        this.extractorBuilder = extractorBuilder;
+    }
+
+    @Nonnull
+    public ChannelTabExtractor getChannelTabExtractor(@Nonnull final StreamingService service) {
+        return extractorBuilder.build(service, new ListLinkHandler(this));
+    }
+}