ICU functions should be cdecl

[Berrysoft]

The ICU functions provided in Windows.Win32.Globalization should be cdecl, but they are now marked as winapi, aka stdcall.

[riverar]

// icu.h
#elif defined(_MSC_VER)
#   define U_EXPORT2 __cdecl
...
U_CAPI UChar32 U_EXPORT2
utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict);

[mikebattista]

I see CallingConvention = CallingConvention.Cdecl inside the DllImport attribute on all these APIs.

Closing out for now. Reactivate if you have more specifics on any requested metadata changes.

[riverar]

Believe this was fixed with #1201