src/include/duckdb/common/assert.hpp: Added winapi

[emmenlau]

When building duckdb with the LLVM ClangCl compiler frontend 13.0.0 in front of Visual Studio 2019 v16.11 and using ninja, I get an error about an undefined symbol:

lld-link: error: undefined symbol: void __cdecl duckdb::DuckDBAssertInternal(bool, char const *, char const *, int)
>>> referenced by C:\BDA\bld\XTJyb_7r\0\duckdb\src\include\duckdb\common\types\string_type.hpp:32
>>>               test\extension\CMakeFiles\loadable_extension_demo.dir\loadable_extension_demo.cpp.obj:(public: __cdecl duckdb::string_t::string_t(char const *, unsigned int))
>>> referenced by C:\BDA\bld\XTJyb_7r\0\duckdb\src\include\duckdb\common\types\vector.hpp:217
>>>               test\extension\CMakeFiles\loadable_extension_demo.dir\loadable_extension_demo.cpp.obj:(public: static bool __cdecl duckdb::ConstantVector::IsNull(class duckdb::Vector const &))
>>> referenced by C:\BDA\bld\XTJyb_7r\0\duckdb\src\include\duckdb\common\types\vector.hpp:222
>>>               test\extension\CMakeFiles\loadable_extension_demo.dir\loadable_extension_demo.cpp.obj:(public: static struct duckdb::ValidityMask & __cdecl duckdb::ConstantVector::Validity(class duckdb::Vector &))
>>> referenced 8 more times

To resolve this error, I have to add the DLL export for DuckDBAssertInternal.

[Mytherin]

Thanks for the PR! Looks good. Failures are unrelated to the PR and related to some other CI hickups we had recently.