[Feat, Test] (MG_Backend/DirectVulkan, MG_Test): Magma advertisement + the parallel-compile test net

Same gated push as the Espryt commit. The tests ride here because they
exercise both backends' advertisement paths and every piece of the
extension: ParallelShaderCompileTest (13 unit cases - the held-job proof
that GL_FALSE is observable and a second poll still shows outstanding work,
program equivalent, untouched objects read TRUE, always-TRUE with async
off, unknown pnames still INVALID_ENUM, zero-count join+inline for compiles
AND links, nonzero restores while Initialize() does not, clamping and
0xFFFFFFFF and KHR/ARB sharing one state, the getter vs the budget, the
string tracking configuration through glGetString AND glGetStringi) and
AsyncCompileScenario (5 real-GPU cases per the design: 64-compile polling,
forced-join correctness, string/thread-count checks against a live driver,
zero-count synchronous settlement, and async-vs-sync frames rendered
byte-identical with quadrant signatures so two identically-wrong images
cannot pass). Verified 5/5 on NVIDIA in the full 2x2 backend x flag matrix
with MOBILEGL_ITEST_REQUIRE_GPU=1.

MobileGL/MG_Test/Program/CMakeLists.txt

@@ -60,6 +60,22 @@ target_link_libraries(
         ${LINK_LIBRARIES}
 )
 
+add_executable(
+        ParallelShaderCompileTest
+        ParallelShaderCompileTest.cpp
+)
+
+target_include_directories(ParallelShaderCompileTest PRIVATE
+        ${MGL_ROOT}/include
+        ${MGL_ROOT}/MobileGL
+)
+
+target_link_libraries(
+        ParallelShaderCompileTest PRIVATE
+        GTest::gtest_main
+        ${LINK_LIBRARIES}
+)
+
 # Its own binary on purpose: this one calls MobileGL::Destroy(), and ShaderCompilePool's
 # stop is a one-way latch for the whole process - every case declared after it in the same
 # binary would silently run its compiles and links inline.
@@ -97,4 +113,6 @@ gtest_discover_tests(ProgramTest DISCOVERY_TIMEOUT 30 PROPERTIES LABELS unit)
 # compile pool so there is something in flight to race against.
 gtest_discover_tests(AsyncCompileTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)
 gtest_discover_tests(AsyncLinkTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)
+# Same reason: the GL_COMPLETION_STATUS_KHR cases saturate a one-worker pool on purpose.
+gtest_discover_tests(ParallelShaderCompileTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)
 gtest_discover_tests(AsyncTeardownTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)