Convert functional tests in taxonomy module to kernel tests

Problem/Motivation

As per #3582242: Convert functional tests with suitably simple HTTP requests to kernel tests but for taxonomy module.

So far this includes 16 tests.

There is a new TaxonomyTestBase in the Kernel namespace, based on the same in the Functional namespace.

There is a new rebuildContainer method in HttpKernelUiHelperTrait. This is so we can still use the same traits that the Functional tests use, that are already calling $this->rebuildContainer.

There was already a Views\TaxonomyTestBase class in the Kernel namespace, so views related conversions switch to using that base class instead of the same in the Functional namespace.

Classes for TaxonomyDefaultArgumentTest and TaxonomyTermArgumentDepthTest already existed in the Kernel namespace, so test methods have simply moved across, rather than moving the whole class.

The conversions were partially (or mostly) performed by Claude Code, but I understand and take responsibility for all the code changes. These words are my own.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet