[Feat] (MG_State, MG_Impl): give program pipelines their object and their state

Every program pipeline entry point was an export stub, and the stub macro's
`return (type)1` made glIsProgramPipeline answer GL_TRUE for anything - including
the names glGenProgramPipelines had never written. All four
direct_state_access.program_pipelines cases failed.

ProgramPipelineObject holds what GL 4.6 core 7.4 says a pipeline is: a program
reference per shader stage, the active program glProgramUniform* addresses, a
validate status and an info log. Its validate status starts false, unlike
ProgramObject's, because a pipeline that has never been validated must report
GL_VALIDATE_STATUS as 0.

The name rules follow the shape queries and transform feedbacks already use, and
which the CTS checks first: glGenProgramPipelines only RESERVES a name and
glIsProgramPipeline answers GL_FALSE for it; the object appears on first bind, or
immediately from glCreateProgramPipelines. Map membership is object existence -
a pipeline, unlike a transform feedback, has no stateful default object zero, so
no everBound flag is needed.

glGet(GL_PROGRAM_PIPELINE_BINDING) reports the real binding now instead of a
hardcoded zero whose comment said the entry points were stubbed.

This is the state half only. program_pipelines_functional needs mixed-stage
rendering - a vertex-only and a fragment-only program drawn together - and stays
failing; glCreateShaderProgramv is deliberately left stubbed until that lands, so
nothing can half-work in between.

Takes program_pipelines_creation, _defaults and _errors from failing to passing
on both backends.

MobileGL/MG_State/GLState/Core.cpp

@@ -802,6 +802,53 @@ namespace MobileGL::MG_State {
                 m_transformFeedbackObjects[id] = {};
             }
         }
+        // Program pipeline
+        void GLContext::GenProgramPipelineNames(Uint number, Vector<Uint>& pipelines) {
+            pipelines.resize(number);
+            // Names only: glIsProgramPipeline must answer GL_FALSE until one is bound or created.
+            m_programPipelineNames.Generate(number, pipelines.data());
+        }
+
+        void GLContext::CreateProgramPipelineObject(Uint index) {
+            m_programPipelines[index] = MakeShared<ProgramPipelineObject>(index);
+        }
+
+        Bool GLContext::ValidateProgramPipelineName(Uint index) const {
+            return index == 0 || m_programPipelineNames.IsValid(index);
+        }
+
+        Bool GLContext::IsProgramPipelineObject(Uint index) const {
+            if (index == 0 || !m_programPipelineNames.IsValid(index)) return false;
+            return m_programPipelines.find(index) != m_programPipelines.end();
+        }
+
+        void GLContext::BindProgramPipelineObject(Uint index) {
+            if (index != 0 && m_programPipelines.find(index) == m_programPipelines.end()) {
+                // First bind is what turns a reserved name into an object.
+                m_programPipelines[index] = MakeShared<ProgramPipelineObject>(index);
+            }
+            m_boundProgramPipeline = index;
+        }
+
+        void GLContext::MarkProgramPipelineForDeletion(Uint index) {
+            if (index == 0 || !m_programPipelineNames.IsValid(index)) return;
+            if (index == m_boundProgramPipeline) {
+                m_boundProgramPipeline = 0;
+            }
+            m_programPipelines.erase(index);
+            m_programPipelineNames.Delete(index);
+        }
+
+        const SharedPtr<ProgramPipelineObject>& GLContext::GetProgramPipelineObject(Uint index) const {
+            static const SharedPtr<ProgramPipelineObject> kNone;
+            const auto it = m_programPipelines.find(index);
+            return it == m_programPipelines.end() ? kNone : it->second;
+        }
+
+        const SharedPtr<ProgramPipelineObject>& GLContext::GetBoundProgramPipeline() const {
+            return GetProgramPipelineObject(m_boundProgramPipeline);
+        }
+
 
         Bool GLContext::ValidateTransformFeedbackName(Uint index) const {
             return index == 0 || m_transformFeedbackNames.IsValid(index);