drm_hwcomposer: clang-tidy: enable cppcoreguidelines-* checks

Our code isn't ready for the following checks therefore keep disabled
-cppcoreguidelines-pro-bounds-array-to-pointer-decay
-cppcoreguidelines-pro-bounds-constant-array-index
-cppcoreguidelines-pro-bounds-pointer-arithmetic
-cppcoreguidelines-pro-type-cstyle-cast
-cppcoreguidelines-pro-type-vararg
-cppcoreguidelines-avoid-magic-numbers
-cppcoreguidelines-macro-usage
-cppcoreguidelines-avoid-c-arrays

+ fixed existing tidy warnings for these checks.

Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
diff --git a/compositor/DrmDisplayCompositor.h b/compositor/DrmDisplayCompositor.h
index ab3f867..92dadca 100644
--- a/compositor/DrmDisplayCompositor.h
+++ b/compositor/DrmDisplayCompositor.h
@@ -143,11 +143,11 @@
 
   ModeState mode_;
 
-  int framebuffer_index_;
+  int framebuffer_index_{};
   DrmFramebuffer framebuffers_[DRM_DISPLAY_BUFFERS];
 
   // mutable since we need to acquire in Dump()
-  mutable pthread_mutex_t lock_;
+  mutable pthread_mutex_t lock_{};
 
   // State tracking progress since our last Dump(). These are mutable since
   // we need to reset them on every Dump() call.