Explicit Resource Management for pg pool client

[hyperair]

Add support for Explicit Resource Management for pg.Pool clients.

This is implemented using [Symbol.dispose] instead of [Symbol.asyncDispose] because client.release() is a synchronous function, not async.

Additionally, add a second property client.destroyOnDispose so that Symbol.dispose supports calling client.release(true). This is useful for a usecase that changes connection parameters in a way that is troublesome to reset upon release to the pool, e.g.

const pool = new Pool({
    database: 'foo',
    user: 'foo',
    password: 'foo',
    port: 5432,

    statement_timeout: 10_000,
});

async function getSlowClient() {
    const client = await pool.connect();
    await client.query("SET statement_timeout = 0");
    client.destroyOnDispose = true;
}

async function performReallySlowQuery() {
    using client = await getSlowClient();

    client.query(`select pg_sleep_for('30 minutes')`);
}

Fixes: #3515

Note: This PR has been rebased on top of #3662, so there are some irrelevant commits until that PR is merged.

[hyperair]

Hmm, looks like eslint needs to be upgraded before it'll parse the using test