[Tests] Add manual picture loader benchmark against the real card hosts (#7288)

* tests: add manual picture loader benchmark against the real card hosts

(cherry picked from commit 588d71d3b9a8278ab98b847802908f322c1035b7)

* tests: address review on picture loader benchmark

- Sandbox via unique app/org names plus Linux-only XDG redirection, derive
  the warm-cache probe and data path from SettingsCache, and bail out when the
  temporary sandbox cannot be created.
- Run each pass with a fresh worker and shut workers down before reading the
  429 counters, so the redirect cache is persisted and no worker thread can
  outlive the stack-local counters or the installed message handler.
- Make s_activeCounters atomic and always forward log output when the previous
  handler is the built-in (nullptr) one.
- Validate --timeout-min, scale the cached-pass budget with --count, honour the
  first --url as the stress template, and add the missing trailing newlines.
- Zero-initialise SettingsCache members so the benchmark mock cannot
  dereference an indeterminate pointer.

---------

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

cockatrice/src/interface/card_picture_loader/card_picture_loader_worker.h

@@ -184,7 +184,7 @@ private:
     /** @brief Returns cached redirect URL for the given original URL, if available. */
     [[nodiscard]] QUrl getCachedRedirect(const QUrl &originalUrl) const;
 
-/** @brief Whether a request for this URL would actually touch the network, rather than being served from the disk
+    /** @brief Whether a request for this URL would actually touch the network, rather than being served from the disk
      * cache. */
     [[nodiscard]] bool requestTouchesNetwork(const QUrl &url) const;