ci: improve CI stability with parallel builds and Valgrind

Major changes:
Run 4 build configurations in parallel with Valgrind on Linux
Add test failure detection verification (meta-test)
Port allocation per build to prevent conflicts in parallel runs
Add --coverage-only flag for dedicated coverage builds
Code quality:

Add TEST_GROUPS constant, CMOCKA patterns, helper functions
Organize ci-build.sh into sections

prof.supp

@@ -8,6 +8,29 @@
 # * python suppressions file from https://github.com/python/cpython/blob/main/Misc/valgrind-python.supp
 #
 
+# ============================================
+# glibc AVX2 optimizations (false positives)
+# See: https://sourceware.org/bugzilla/show_bug.cgi?id=19796
+# ============================================
+
+{
+  glibc_wcpncpy_avx2
+  Memcheck:Addr32
+  fun:__wcpncpy_avx2
+  fun:wcsxfrm_l
+  fun:g_utf8_collate_key
+  ...
+}
+
+{
+  glibc_wcsxfrm_avx2
+  Memcheck:Addr32
+  ...
+  fun:wcsxfrm_l
+  fun:g_utf8_collate_key
+  ...
+}
+
 # ============================================
 # Functional tests suppressions (stabber/pthread)
 # ============================================