Recognize ixx as part of the cpp suffix (#26333)

Adds "ixx" as path suffix to be recognized for c++. 

> ixx documentation
https://learn.microsoft.com/en-us/cpp/cpp/modules-cpp?view=msvc-

I've also added it to the icon file. 

Release Notes:

- N/A

crates/languages/src/cpp/config.toml

@@ -1,6 +1,6 @@
 name = "C++"
 grammar = "cpp"
-path_suffixes = ["cc", "hh", "cpp", "h", "hpp", "cxx", "hxx", "c++", "ipp", "inl", "cu", "cuh", "C", "H"]
+path_suffixes = ["cc", "hh", "cpp", "h", "hpp", "cxx", "hxx", "c++", "ipp", "inl", "ixx", "cu", "cuh", "C", "H"]
 line_comments = ["// ", "/// ", "//! "]
 autoclose_before = ";:.,=}])>"
 brackets = [