Fix MSVC warning C4141 ('inline' used more than once)
Bug: On MSVC sf_always_inline expands to ```__forceinline```, which already implies ```inline```, so definitions writing both triggered "warning C4141 ('inline' used more than once)".
Fix: Moved ```inline``` into the macro and removed it from all definition sites.
GCC/Clang still get ```inline __attribute__((always_inline))```. ```inline``` is in the macro since the attribute alone would not set linkage.
[Edit]
Also adds MSVC coverage to CI as requested.
closes https://github.com/official-stockfish/Stockfish/pull/7078
No functional change