This will allow to omit parameters with unspecified types

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

also simplifies the code and now exactly matches postgresql search rules

When the connection is lost or is closed, subsequent transaction will no longer be nested because they started in a brand new session. Our internal representation of the nesting shold take this into account

Internally, ArrayStatement expects every row to be represented as an array regardless of the fetch mode, however FetchMode::COLUMN produces one value per row.

fetch() is part of the ResultStatement interface. Using Statement as a
type declaration needlessly constrains people to use this class only
with implementations of Statement.

The failures are caused by the changes in PHP according to https://wiki.php.net/rfc/notice-for-non-valid-array-container.

Change "we're" to "where" in docblock for listTableColumns()
method. Add comma to improve readability.

The method is not used for anything else than skipping tests for specific drivers. Cross-driver portability should be established by drivers, not outside of them based on their name.