Cleanup: Clang-Tidy, modernize-use-using

Replace `typedef` with `using` in C++ code.

In the case of `typedef struct SomeName { ... } SomeName;` I removed the
`typedef` altogether, as this is unnecessary in C++. Such cases have been
rewritten to `struct SomeName { ... };`

No functional changes.

.clang-tidy

@@ -37,7 +37,6 @@ Checks:  >
   -modernize-avoid-c-arrays,
   -modernize-use-equals-default,
   -modernize-use-nodiscard,
-  -modernize-use-using,
   -modernize-loop-convert,
   -modernize-pass-by-value,
   -modernize-use-default-member-init,