Windows / MSVC build errors

[tlemo]

The latest MSVC (19.41.34120, included with Visual Studio 2022), reports a few build issues in test-pad-reflect-1d.cpp:

ggml\tests\test-pad-reflect-1d.cpp(28): error C7555: use of designated initializers requires at least '/std:c++20'
ggml\tests\test-pad-reflect-1d.cpp(89): error C7555: use of designated initializers requires at least '/std:c++20'
ggml\tests\test-pad-reflect-1d.cpp(88): error C4576: a parenthesized type followed by an initializer list is a non-standard explicit type conversion syntax
ggml\tests\test-pad-reflect-1d.cpp(148): error C7555: use of designated initializers requires at least '/std:c++20'
ggml\tests\test-pad-reflect-1d.cpp(147): error C4576: a parenthesized type followed by an initializer list is a non-standard explicit type conversion syntax