Initial BlockExt trait

[edg-l]

Here is the first pr with some utility methods as discussed in #616 , extending it should be easy, also feel free to refactor it or use another name, folder, etc.

I added it behind a feature, because it requires the ods feature.

[raviqqe]

@edg-l It doesn't have to be in this PR but what do you think of splitting the trait into different dialects for extensibility? For example,

pub trait SimpleBlock<'ctx> {
    fn arg(&self, idx: usize) -> Result<Value<'ctx, '_>, Error>;
}

pub trait ArithBlock<'ctx> {
    fn addi(
        &self,
        lhs: Value<'ctx, '_>,
        rhs: Value<'ctx, '_>,
        location: Location<'ctx>,
    ) -> Result<Value<'ctx, '_>, Error>;

    // ...
}

pub trait LlvmBlock<'ctx> {
    fn insert_value(&self, /* ... */) -> Result<Value<'ctx, '_>, Error>;

    // ...
}

And, then users select dialects' block traits as needed:

use melior::block_ext::ArithBlock;
// ...

fn main() {
  // ...

  let z = block.addi(x, y);

  // ...
}

[edg-l]

I would use ArithBlockExt as a better name because maybe others can confuse it for a Block but i agree with the idea

[raviqqe]

@edg-l do you think actually it's possible to generate these block extensions automatically like the ODS dialects API?

[edg-l]

@edg-l do you think actually it's possible to generate these block extensions automatically like the ODS dialects API?

Hm probably not since they have some (little) logic in it often

[raviqqe]

Thank you for the changes!