[PATCH 0/4] MR3681: include: Deduplicate WineTest helpers. 1/2

[Rémi Bernon (＠rbernon)]

First MR to begin de-duplicating WineTest helpers.

The idea is to make most helpers static inline, and the counters extern, prefixing any variable moved to the global scope. This will allow dinput / ntoskrnl driver tests to re-use the helpers by only having to provide the counters and an implementation of `winetest_get_thread_data` / `winetest_vprintf` (and a couple of other functions).

Then, it will also be re-usable in WinRT tests for https://gitlab.winehq.org/wine/wine/-/merge_requests/3643.