[CI] Address miscellaneous Bazel / Clang build failures (#4344)

- Adds an explicit dependency for headers used in `TorchMLIRInitAll`
- Addresses a `std::accumulate` usage issue:
https://godbolt.org/z/xs441Ebfe

Signed-off-by: Artem Gindinson <[email protected]>

Author: AGindinson

lib/RefBackend/RefBackend.cpp

@@ -109,7 +109,7 @@ static std::string getConsumeReturnFunctionNameForReturnTypes(TypeRange types) {
     tokens.push_back(getTypeToken(type));
 
   return std::accumulate(tokens.begin(), tokens.end(), std::string(),
-                         [](std::string &a, std::string &b) {
+                         [](std::string a, std::string b) {
                            return a.empty() ? b : (a + "_" + b);
                          });
 }

utils/bazel/torch-mlir-overlay/BUILD.bazel

@@ -909,6 +909,7 @@ cc_library(
         "@llvm-project//mlir:AllExtensions",
         "@llvm-project//mlir:Dialect",
         "@llvm-project//mlir:DialectUtils",
+        "@llvm-project//mlir:FuncExtensions",
         "@llvm-project//mlir:IR",
         "@llvm-project//mlir:TensorInferTypeOpInterfaceImpl",
         "@stablehlo//:linalg_passes",