[GH-3777] Don't remove composer lock travis on stable 2.10 branch

Allow build failures for unstable dependencies

Switched from PHPBrew-based configuration to the Docker-based

As per the support response, continuousphp switched to building their containers based on the official images from PHP.

Remove temporary SQLite file on teardown

Update deprecation messages to refer to DBAL

Replace DefaultTypes with Types in type constant deprecation annotations

New deprecations for 2.10

add missing exit codes to ensure Symfony 5 compatibility

Don't skip a test for sqlite

Relax statement type declaration

Updated SQL Server extensions to fix build failures on PHP 7.4

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

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.

Add missing MySQL 8.0 reserved keywords

Quote collation on MySQL