Expose lock_with_behavior from the QuerySelect

[GrandChaman]

Motivation

As of now, if one wants to fetch a row using the FOR UPDATE SKIP LOCKED clauses, one need to write something that looks like that:

let mut select = Entity::find_by_id(id);

QuerySelect::query(&mut select) // Many traits have the `query` method, so we need to differentiate here.
    // This returns a `&mut SelectStatement`, which cannot be chained with the implementors of `QuerySelect`.
    // So we have to write it on a separate line.
    .lock_with_behavior(LockType::Update, LockBehavior::SkipLocked);

select
        .one(conn)
        .await

Proposed Solutions

This is a minor issue of course, but could be alleviated fairly easily by exposing the .lock_with_behavior directly from the QuerySelect trait.

A PR will follow to address this issue.

Current Workarounds

The attached example demonstrates the current workaround.