Lazily inject the database connection into DbLog

Problem/Motivation

DbLog requires a database connection, but initializing a logger often doesn't mean you are actually going to log anything.

In 📌 Replace calls to ::expectWarning*() in Drupal\Tests\user\Kernel\Views\HandlerFilterRolesTest Fixed and similar issues we have discussed lazily injecting loggers, but end users of loggers should not really be concerned about this; a better option would be to only instantiate the database connection when we have something to log.

Steps to reproduce

Proposed resolution

Inject Connection via a service closure into DbLog.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet