Support Set as bind parameter

**Is your feature request related to a problem? Please describe.**

I tried to pass a `Set` as a bind parameter, expecting it to behave like `Array`. It was hard to debug since the query gave wrong results, not an error.

**Describe the solution you'd like**

Support `Set` just like `Array`: convert it to a Postgres array.

**Additional context**

Set:

```console
$ deno eval 'import { Client } from "https://deno.land/x/postgres@v0.19.3/mod.ts"; const client = new Client({}); await client.connect(); const odds = new Set([1,3,5]); const result = await client.queryObject`SELECT 3=ANY(${odds}) AS should_be_true`; console.log(result.rows);'
[ { should_be_true: false } ]
```

Array:

```console
$ deno eval 'import { Client } from "https://deno.land/x/postgres@v0.19.3/mod.ts"; const client = new Client({}); await client.connect(); const odds = new Array([1,3,5]); const result = await client.queryObject`SELECT 3=ANY(${odds}) AS should_be_true`; console.log(result.rows);'
[ { should_be_true: true } ]
```