Migrate to current Roc syntax

[niclas-ahden]

• No backpassing
• New record builders
• PNC
• snake_case

The API changes from:

    |> Pg.Cmd.expectN (
        Pg.Result.succeed {
            name: <- Pg.Result.str "name" |> Pg.Result.apply,
            price: <- Pg.Result.dec "price" |> Pg.Result.apply
        }
    )

To:

|> Pg.Cmd.expect_n(
    { Pg.Result.record_builder <-
        name: Pg.Result.str("name"),
        price: Pg.Result.dec("price"),
    },
)

Note Pg.Result.record_builder above. Pg.Cmd.succeed can still be used to return non-records like so:

|> Pg.Cmd.expect_n(
    Pg.Result.succeed(
        |name|
            |age|
                age_str = Num.to_str(age)
                "${name}: ${age_str}",
    )
    |> Pg.Result.with(Pg.Result.str("name"))
    |> Pg.Result.with(Pg.Result.u8("age")),
)

It's unclear to me whether this is desirable. However, given that the name Pg.Result.succeed is taken, I opted for
Pg.Result.record_builder for the records to make it discoverable and understandable.

This PR also includes the changes from #10 and #11.

This is a partial migration as I ran out of steam part-way through sql-cli and examples/store. I stopped when faced with the query builder and its use of the old record builders. There were no brain cells left over to start pondering that design. Hopefully this offering can still be helpful as a stepping stone toward current Roc!

[agu-z]

@niclas-ahden Thank you so much for all the effort you put into this. I'm going to clean up a few other things and make a release!