feat: LEP-001 Introduce Lake Context

[khorolets]

Implements #54

We will have two methods in Lake:

• run() that accepts a user-defined function that expects only the Block
• run_with_context() that accepts a user-defined function and a Context.

fn main() -> anyhow::Result<()> {
    struct MyContext {
        pub my_field: String,
    }

    let context = MyContext {
       my_field: "my_value".to_string(),
    };

    near_lake_framework::LakeBuilder::default()
        .testnet()
        .start_block_height(112205773)
        .build()?
        .run_with_context(handle_block, &context)
}

async fn handle_block(
    _block: near_lake_primitives::block::Block, 
    context: &MyContext
) -> anyhow::Result<()> { 
    Ok(())
}

After that, the user-defined function (handle_block in my example) will be receiving the reference to the context user has provided on each block.

This PR still requires a few clean-ups, and documentation updates before it can be reviewed.

[eduohe]

Not sure what is alwaya, maybe a typo here?

[eduohe]

Just a small potential typo, but looks good

[morgsmccauley]

Nice!