Fix a few small Windows / MSVC build issues

[tlemo]

The latest MSVC reports a few compilation problems (#1194)

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

[slaren]

It would be preferable to fix the code to require only C++17, rather than changing the standard which will create more issues with compilers that still do not support C++20.

[tlemo]

It would be preferable to fix the code to require only C++17, rather than changing the standard which will create more issues with compilers that still do not support C++20.

Sure. I updated the changes to fix the MSVC build and stick to C++17.