drm_hwcomposer: CI: Bump-up clang toolchain to v15

Address new clang-tidy findings, in most cases 'misc-const-correctness'
check was addressed by adding 'const' modifier, or in some cases changed
to 'auto' (where it's better for formatting).

Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
diff --git a/utils/Worker.cpp b/utils/Worker.cpp
index d2b60c8..e1c7aee 100644
--- a/utils/Worker.cpp
+++ b/utils/Worker.cpp
@@ -30,7 +30,7 @@
 }
 
 int Worker::InitWorker() {
-  std::lock_guard<std::mutex> lk(mutex_);
+  const std::lock_guard<std::mutex> lk(mutex_);
   if (initialized())
     return -EALREADY;