core: redo search cache from scratch. resolves #10382 (#10447)

In simple words, when you make a request in Jackett, the results are saved in memory (cache). The next request will return results form the cache improving response time and making fewer requests to the sites.
* We assume all indexers/sites are stateless, the same request return the same response. If you change the search term, categories or something in the query Jackett has to make a live request to the indexer.
* There are some situations when we don't want to use the cache:
** When we are testing the indexers => if query.IsTest results are not cached
** When the user updates the configuration of one indexer => We call CleanIndexerCache to remove cached results before testing the configuration
** When there is some error/exception in the indexer => The results are not cached so we can retry in the next request
* We want to limit the memory usage, so we try to remove elements from cache ASAP:
** Each indexer can have a maximum number of results in memory. If the limit is exceeded we remove old results
** Cached results expire after some time
* Users can configure the cache or even disable it

README.md

@@ -676,7 +676,7 @@ Jackett is available as a beta package from [SynoCommunity](https://synocommunit
 
 
 ## Running Jackett behind a reverse proxy
-When running jackett behind a reverse proxy make sure that the original hostname of the request is passed to Jackett. If HTTPS is used also set the X-Forwarded-Proto header to "https". Don't forget to adjust the "Base Path Override" Jackett option accordingly.
+When running jackett behind a reverse proxy make sure that the original hostname of the request is passed to Jackett. If HTTPS is used also set the X-Forwarded-Proto header to "https". Don't forget to adjust the "Base path override" Jackett option accordingly.
 
 Example config for apache:
 ```