refactor: make BaseService and BaseCollector abstract

[samsonasik]

Description

This PR target to 4.8, change 2 files:

• system/Config/BaseService.php
• system/Debug/Toolbar/Collectors/BaseCollector.php

in the system or tests, they never instantiated, only extended, verified with structarmed ExtendedClassMustBeAbstractOrInstantiatedRule for future new Base+ prefix classes to be abstract.

->layerPattern('BaseClasses', '/^CodeIgniter\\\\.*Base.*$/')
->rule('base_classes.must_be_abstract', new ExtendedClassMustBeAbstractOrInstantiatedRule('BaseClasses'))

If you want to only apply the changes class change only to easier for back and forth develop and 4.8 branch, just let me know ;)

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[samsonasik]

Ready for review 👍