There are checks to urls that attempt to limit recurrsion when
parse_file is called. This is problematic for css import urls that
can call an indefinite amount of nested import urls. An import limit
has been introduced to address this. Fragments have also been removed.

The only changes to requirements since Moodle 4.3 are increases to:

* the minimum PHP version required; and
* the minimum required Moodle version.

* Feature: We can use a minimum grade different than zero
  - Use correct minimum input values.
  - Use data generators for faster test execution.
* Scenario: Disable category overriding
  - Use the field name to ensure that the correct field is being tested.

Cherry-picked from MDL-79062.

This hack was introduced to work around a bug in MySQL 5.6.14 and
MariaDB at the time.

https://bugs.mysql.com/bug.php?id=69882

It was addressed a few months later in 5.6.16, and 5.7.4.
MariaDB merged version 5.6.16 of MySQL's InnoDB engine in MariaDB
10.0.11 and got hte patch from there.

Moodle has required MariaDB 10.2.29 since Moodle 3.9 and it is therefore
safe to remove these hacks for MariaDB.
MySQL is also affected for version 5.7.0 >= MySQL < 5.7.4.