[MLIR][NFC] Ignore clang-tidy modernize-use-using check in C code (#180326)

In the MLIR C API headers, clang-tidy’s `modernize-use-using` check
reports a large number of type definitions that use `typedef`. In my
IDE, this even causes the `typedef` code to be shown as struck through.
However, in this case it is clearly not possible to replace them with
`using`. This PR suppresses the `modernize-use-using` check for the code
inside `extern "C"` blocks.

mlir/.clang-tidy

@@ -58,3 +58,5 @@ CheckOptions:
     value:           camelBack
   - key:             readability-identifier-naming.VariableCase
     value:           camelBack
+  - key:             modernize-use-using.IgnoreExternC
+    value:           true