[clang] [llvm] Forward declare TextEncodingConverter in TextEncoding.h, move config.h into TextEncoding.cpp (PR #207382)

[Abhina Sree via cfe-commits]

================
@@ -27,5 +29,5 @@ class TextEncoding {
 
   llvm::StringRef getLiteralEncoding() { return LiteralEncoding; }
 };
-} // namespace clang
+
 #endif
----------------
abhina-sree wrote:

Do you mean keep the changes in this PR? https://github.com/llvm/llvm-project/pull/207247
I rebased to include them, please let me know if you meant I need to make different changes, thanks!

https://github.com/llvm/llvm-project/pull/207382