Initial implementation for decl-tree reflection API (#4666)

* Initial implementation for decl-tree reflection API

This patch adds Slang API methods for walking all the declarations in the AST.

We expose this functionality through an abstract `DeclReflection` class that can be a type, function or a variable declaration.
We also provide ways to cast the decl to a `FunctionReflection`, `TypeReflection` or `VariableReflection` and traverse through the child nodes (for instance, a struct type will have component variable declarations)

This patch also adds `ISlangInternal` as an internal COM interface to allow us to cast IGlobalSession to the internal Session pointer while bypassing any wrappers (such as the capture interface)

* Update slang.h

* Remove `ISlangInternal` (its causing a diamond pattern w.r.t `ISlangUnknown`) and use `ComPtr` for proper ref management.

* Update unit-test-decl-tree-reflection.cpp

* Change `FunctionDeclBase` to use `DeclRef` instead of directly using the decl.

* Update slang-reflection-api.cpp

1 files changed, 16 insertions, 4 deletions

diff --git a/source/slang-capture-replay/slang-global-session.cpp b/source/slang-capture-replay/slang-global-session.cpp
index b8dfd7d40..d8f1e361d 100644
--- a/source/slang-capture-replay/slang-global-session.cpp
+++ b/source/slang-capture-replay/slang-global-session.cpp
@@ -28,11 +28,23 @@ namespace SlangCapture
         m_actualGlobalSession->release();
     }
 
-    ISlangUnknown* GlobalSessionCapture::getInterface(const Guid& guid)
+    SLANG_NO_THROW SlangResult SLANG_MCALL GlobalSessionCapture::queryInterface(SlangUUID const& uuid, void** outObject) 
     {
-        if(guid == ISlangUnknown::getTypeGuid() || guid == IGlobalSession::getTypeGuid())
-            return asExternal(this);
-        return nullptr;
+        if (uuid == Session::getTypeGuid())
+        {
+            // no add-ref here, the query will cause the inner session to handle the add-ref.
+            this->m_actualGlobalSession->queryInterface(uuid, outObject);
+            return SLANG_OK;
+        }
+
+        if (uuid == ISlangUnknown::getTypeGuid() && uuid == IGlobalSession::getTypeGuid())
+        {
+            addReference();
+            *outObject = static_cast<slang::IGlobalSession*>(this);
+            return SLANG_OK;
+        }
+
+        return SLANG_E_NO_INTERFACE;
     }
 
     SLANG_NO_THROW SlangResult SLANG_MCALL GlobalSessionCapture::createSession(slang::SessionDesc const&  desc, slang::ISession** outSession)