Revert "Add type confusion protection to the default memory provider."

This reverts commit d56201e28d.

src/ds/helpers.h

@@ -42,25 +42,6 @@ namespace snmalloc
     }
   };
 
-  /**
-   * A singleton global.  Used to allow globals in headers.  Precisely one
-   * instance of the static field will exist in the final program, irrespective
-   * of the number of compilation units that reference the field.
-   *
-   * C++ globals do not have their types as part of the name mangling, so this
-   * allows a singleton instance of a specific type that won't be confused with
-   * other template instantiations of the same type.
-   */
-  template<class T>
-  struct TypedSingleton
-  {
-    /**
-     * The global variable, which will have a mangled name that includes the
-     * type of `T`.
-     */
-    static inline T global;
-  };
-
   /**
    * Wrapper for wrapping values.
    *