Convert functions to const in math and tick utils

Functions in the `sqrt_price_math.rs` and `nearest_usable_tick.rs` files, as well as the `constants.rs` file, were changed from regular to `const` functions. This provides the capacity to have these functions evaluated at compile time wherever their usage throughout the codebase makes it possible for constant evaluation. Also, updated the tick comparison in `nearest_usable_tick.rs` which ensures more readability.

src/constants.rs

@@ -18,7 +18,7 @@ pub enum FeeAmount {
 
 impl FeeAmount {
     /// The default factory tick spacings by fee amount.
-    pub fn tick_spacing(&self) -> i32 {
+    pub const fn tick_spacing(&self) -> i32 {
         match self {
             Self::LOWEST => 1,
             Self::LOW => 10,

src/utils/nearest_usable_tick.rs

@@ -9,9 +9,9 @@ use super::tick_math::{MAX_TICK, MIN_TICK};
 ///
 /// returns: i32
 ///
-pub fn nearest_usable_tick(tick: i32, tick_spacing: i32) -> i32 {
+pub const fn nearest_usable_tick(tick: i32, tick_spacing: i32) -> i32 {
     assert!(tick_spacing > 0, "TICK_SPACING");
-    assert!((MIN_TICK..=MAX_TICK).contains(&tick), "TICK_BOUND");
+    assert!(tick >= MIN_TICK && tick <= MAX_TICK, "TICK_BOUND");
     let rounded = tick.div_floor(tick_spacing) * tick_spacing;
     let rounded = rounded + (tick - rounded + tick_spacing / 2) / tick_spacing * tick_spacing;
     if rounded < MIN_TICK {

src/utils/sqrt_price_math.rs

@@ -17,7 +17,7 @@ fn to_uint160(x: U256) -> Result<U256, UniswapV3MathError> {
     }
 }
 
-fn to_uint256(x: u128) -> U256 {
+const fn to_uint256(x: u128) -> U256 {
     U256::from_limbs([x as u64, (x >> 64) as u64, 0, 0])
 }