[Shaders] Allow constants and expressions in `hint_range`

[Chaosus]

Allows expressions in hint_range declaration:

shader_type spatial;

const float begin = 0.5;
const float end = 4.0;
const float st = 0.1;

uniform float test : hint_range(begin, end);
uniform float test2 : hint_range(0.25 + 0.25, TAU + 1.0, st);

• Fix https://github.com/godotengine/godot/issues/101926

[maxpiepenbrink]

big fan of this

[Repiteo]

Thanks!

[geekley]

The hints instance_index and hint_enum also accept parameters. Should we assume they may eventually allow expressions or at least named constants as well? I guess not with hint_enum, since only strings are allowed, and we can't set those in constants (except for macros). But what about instance_index?