Add `PRINT_VERBOSE` macro alongside the function

[aaronfranke]

In the Godot core team meeting on 2025-05-07, it was discussed that PR https://github.com/godotengine/godot/pull/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 https://github.com/godotengine/godot/pull/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.

[dsnopek]

For this to really be worth it peformance-wise, I think we should also be statically caching the verbose flag in godot::is_print_verbose_enabled().

So, changing it to look like:

bool is_print_verbose_enabled() {
	static bool verbose_enabled = OS::get_singleton()->is_stdout_verbose();
	return verbose_enabled;
}

Otherwise, we're making two calls across the GDExtension <-> Godot boundary instead of just one: the first to check OS::get_singleton()->is_stdout_verbose() and the 2nd to do print_line(), and that could actually be slower than the non-macro version