Rework chache handling

* No longer provide multiple HTTP helper functions with the same name
* Default to cache not being used
* Explicitly use the cache for certain Twitch actions and conditions
* Clear caches on shutdown to avoid leaks being reported

plugins/twitch/points-reward-selection.cpp

@@ -136,7 +136,7 @@ TwitchPointsRewardSelection::GetPointsRewards(
 
 	auto response = SendGetRequest(*token, "https://api.twitch.tv",
 				       "/helix/channel_points/custom_rewards",
-				       params);
+				       params, true);
 
 	if (response.status != 200) {
 		blog(LOG_WARNING,