refactor: address clippy warnings and improve code quality (#409)

- Fix string formatting with modern interpolation syntax
- Improve Debug implementation with finish_non_exhaustive()
- Fix function placement in shape.rs to avoid items_after_statements warning
- Use more idiomatic Rust patterns (map_or_else, next_back)
- Clean up conditional imports in vi.rs
- Convert multiple methods to `const` functions for optimization and consistency
- Introduce `core_maths` for enhanced no-std compatibility
- Update `Cargo.toml` for the new optional dependency and feature adjustments

src/layout.rs

@@ -2,10 +2,12 @@
 
 use core::fmt::Display;
 
+use crate::{math, CacheKey, CacheKeyFlags, Color};
 #[cfg(not(feature = "std"))]
 use alloc::vec::Vec;
 
-use crate::{math, CacheKey, CacheKeyFlags, Color};
+#[cfg(not(feature = "std"))]
+use core_maths::CoreFloat;
 
 /// A laid out glyph
 #[derive(Clone, Debug)]
@@ -78,8 +80,8 @@ impl LayoutGlyph {
             self.glyph_id,
             self.font_size * scale,
             (
-                (self.x + x_offset) * scale + offset.0,
-                math::truncf((self.y - y_offset) * scale + offset.1), // Hinting in Y axis
+                (self.x + x_offset).mul_add(scale, offset.0),
+                math::truncf((self.y - y_offset).mul_add(scale, offset.1)), // Hinting in Y axis
             ),
             self.font_weight,
             self.cache_key_flags,