Add PRINT_VERBOSE macro alongside the function

[aaronfranke]

In the Godot core team meeting on 2025-05-07, it was discussed that PR godotengine/godot#100224 is a massive codebase-wide change that will conflict with many PRs and break compatibility with third-party modules. Therefore, there is a lot of hesitation with merging it for a minor improvement, which is itself not unanimously agreed on.

However, there is still the problem of the name conflict in godot-cpp GDExtension, which currently uses a work-around of using a function instead of a macro. This means that print_verbose in godot-cpp has different behavior compared to the macro in the engine, and is objectively slower for no good reason.

Because of this, I opened PR godotengine/godot#106147 to add PRINT_VERBOSE, but @akien-mga suggested that if godot-cpp is the main motivation for making this change, we should see if the problem can be solved in godot-cpp.

This PR adds a capitalized PRINT_VERBOSE macro in parallel with the print_verbose function. This allows godot-cpp users to get the performance benefits of the macro. If users want to write C++ code that is compatible with both in-engine C++ and godot-cpp GDExtension C++, it is trivial to use PRINT_VERBOSE in an engine module like this:

#if GODOT_MODULE
#define PRINT_VERBOSE print_verbose
#endif // GODOT_MODULE

Alternate design to consider: GODOT_PRINT_VERBOSE as the name.