Tests: bundle tests for some modules in their own executables

The ffmpeg, guardedalloc and blenlib are quite isolated and putting them in
their own executable separate from blender_test is faster for development than
linking the entire blender_tests executable.

For Cycles, this also bundles all the unit tests into one executable.

Ref T79958

Differential Revision: https://developer.blender.org/D8714

intern/guardedalloc/CMakeLists.txt

@@ -92,5 +92,5 @@ if(WITH_GTESTS)
     bf_blenlib
   )
   include(GTestTesting)
-  blender_add_test_lib(bf_intern_guardedalloc_tests "${TEST_SRC}" "${INC};${TEST_INC}" "${INC_SYS}" "${LIB};${TEST_LIB}")
+  blender_add_test_executable(guardedalloc "${TEST_SRC}" "${INC};${TEST_INC}" "${INC_SYS}" "${LIB};${TEST_LIB}")
 endif()