fix begin trasaction after reconnect

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

Add support for DISTINCT clause

Fixed query result caching when FetchMode::COLUMN is used

Updated PHPUnit to 8.4.1

$ composer update phpunit/phpunit --with-all-dependencies

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

Temporarily disable the usage of PHPUnit 8.4 due to a regression

See https://github.com/sebastianbergmann/phpunit/issues/3879

Add missing MySQL 8.0 reserved keywords

Quote collation on MySQL

Phpstan fix backport

Updated PHPStan to v0.11.15

Refactor usage of MockBuilder's deprecated setMethods()

Marked connection exception test incomplete on MySQL 8

Fix Appveyor builds

Support for comments on table in all databases

Fix typo in docblock

Using command line options to configure MySQL 8 instead of mounting a config file

Fixed test failures on PHP 7.4

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

Bumped PHPUnit requrement to ^8.3.3, removed dependency on symfony/phpunit-bridge

Switched from ibmcom/db2express-c to ibmcom/db2

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

Add commit result bool