Chore: Use enum for handling `order_by` in website and API

[0ex-d]

I suggest using BidsOrderBy enum Option<BidsOrderBy> (or generic OrderBy enum) to properly handle sorting in the api. This would in turn eliminate the need for some extra type conversions and more clarity.

helix/crates/common/src/api/data_api.rs

Lines 16 to 17 in f26f257

	pub order_by: Option<i8>,
	}

helix/crates/database/src/postgres/postgres_db_service.rs

Lines 1585 to 1590 in f26f257

	if let Some(order) = filters.order() {
	query.push_str(" ORDER BY block_submission.value ");
	query.push_str(if order >= 0 { "ASC" } else { "DESC" });
	} else {
	query.push_str(" ORDER BY block_submission.slot_number DESC");
	}

We can also improve the get_delivered_payloads logic by eliminating

query.push_str(if order >= 0 { "ASC" } else { "DESC" });