Pass values by reference for FPDecimal methods, and associate functions

[DrunkenRandomWalker]

#[allow(clippy::upper_case_acronyms)]
#[derive(Copy, Clone, Default, Debug, PartialEq, Eq, PartialOrd, Ord, JsonSchema)]
pub struct FPDecimal {
    #[schemars(with = "String")]
    pub num: U256,
    pub sign: i8,
}

FPDecimal implemented Copy trait, parameter in associated functions in below are passed parameters by value. So values are copied, I think we are safe to pass parameters by reference, and copy when it is necessary.

cw-injective/packages/injective-math/src/fp_decimal/mod.rs

Lines 116 to 121 in cb5b322

	pub fn _int(x: FPDecimal) -> FPDecimal {
	let x1 = x.num;
	let x1_1 = x1 / FPDecimal::ONE.num;
	let x_final = x1_1 * FPDecimal::ONE.num;
	FPDecimal { num: x_final, sign: x.sign }
	}

cw-injective/packages/injective-math/src/fp_decimal/mod.rs

Lines 131 to 137 in cb5b322

	pub fn _fraction(x: FPDecimal) -> FPDecimal {
	let x1 = x.num;
	FPDecimal {
	num: x1 - FPDecimal::_int(x).num,
	sign: x.sign,
	}
	}