The PHP_CodeSniffer @codingStandardsIgnore annotations are deprecated
and, since version 3.x, the new // phpcs:ignore comments should be used
instead.
This commits just reviews all the uses in core, replacing them for
the better new candidate, or removing when no longer needed.
Implemented with moodle_read_slave_trait
Functionality is triggered by supplying config dboption['readonly'].
See config-dist.php for more info on supported dboptions.
pgsql and mysqli drivers are using this feature. Also added support for
connection timeout for these two drivers.