Introduce a ConnectionParameters value object to store database connection parameters

Problem/Motivation

Database connection configuration is stored in arrays that are more or less taken as is from info in the $databases array in settings.php.

This makes the entire management of these connection options a bit sparsed around, and static analysis struggling.

Proposed resolution

Introduce a ConnectionParameters object where configuration is read from settings.php (or programmatically), then sealed off for the rest of the request. Adjust code so that as much of the logic as possible determines the object before instantation (i.e. end up with a value object).

• Introduce ConnectionParametersInterface and an abstract base class implementation ConnectionParametersBase
• Implement only SQLite in this issue (to demonstrate other drivers can work without), implement the rest drivers in follow ups
• To support BC, db drivers that implement a ConnectionParameters class will start using the new logic, those that don't will get a closure wrapper implementation of ConnectionParametersBase that provides access to the options array
• For the moment, allow read-only array access to the parameters in the new class - this can be deprecated once all drivers are converted
• Deprecate Database::getConnectionInfoAsUrl() and Connection::createUrlFromConnectionOptions() as now the URL version of the parameters can be got from the object directly.
• Ensure new classes are PHPStan level-10 compliant.

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet