Add support for Postgres placeholders to Parser

[sweoggy]

Q	A
Type	improvement
Fixed issues

Summary

This PR enables using Postgres placeholders $# with doctrine/dbal. For example the following query work after this patch:

$connection->executeStatement(
    'INSERT INTO dummy_table (some_id) VALUES ($1)',
    [1],
    [],
);

Without this patch a driver exception is thrown: Could not find parameter 1 in the SQL statement.

[sweoggy]

Replaced by #6634