[clang] [clang] Split up `SemaDeclAttr.cpp` (PR #93966)

[Vlad Serebrennikov via cfe-commits]

================
@@ -14,9 +14,11 @@
 #define LLVM_CLANG_SEMA_SEMASYCL_H
 
 #include "clang/AST/Decl.h"
+#include "clang/AST/DeclBase.h"
----------------
Endilll wrote:

We definitely can, but can I leave it for a follow-up? It wasn't introduced in this pathc, and I have a significant amount of clean-up to do across Sema anyway, where such change would fit nicely.

https://github.com/llvm/llvm-project/pull/93966