Replace fn Offset::is_large() with const Offset::IS_LARGE.

[HaoYang670]

Just as what we have done in arrow-rs: apache/arrow-rs#1664, we can use const to represent offset::is_large:

pub trait Offset: super::private::Sealed + Index {
    /// Whether it is `i32` (false) or `i64` (true).
    const IS_LARGE: bool;
}

impl Offset for i32 {
    const IS_LARGE: bool = false;
}

impl Offset for i64 {
    const IS_LARGE: bool = true;
}

[HaoYang670]

@jorgecarleitao Do we need this change? Or inline function is good enough?

[jorgecarleitao]

Thanks @HaoYang670! It is a constant, so I agree that it is better represented as a const 👍

[HaoYang670]

I will file a PR this weekend. It is my pleasure to contribute to Arrow2 !!

[jorgecarleitao]

Awesome, thanks a lot 🙇