* test: [wip] add tests for rendererChildren
* chore: use serializeInner for clearer output
* fix: should remove the text node if content is empty
* test: also test for appended content
* test: inserting & removing
* test: moving children
* refactor: use a helper function
* test: finish tests
* test: duplicate keys tests belong to keyed children block
* fix(runtime-test): fix insert when moving node in the same parent
* fix: fix failing test cases for rendererChildren
* test: handle rendererChildren edge case
