Revert "_DefaultTabControllerState should dispose all created TabContoller instances. (#136608)" (#144579)

This reverts commit 9fa9fd36.

Fixes https://github.com/flutter/flutter/issues/144087.
Fixes https://github.com/flutter/flutter/issues/138588.

This crash has been reported previously from a customer in google3 in https://github.com/flutter/flutter/issues/138588, but we weren't able to track it down. Thankfully, a repro was now provided in https://github.com/flutter/flutter/issues/144087#issuecomment-1968257383 which traced the crash down to a change made in #136608. This PR reverts that change to fix that crash for now. I will post a new PR shortly that will add a test to cover the use case that caused the crash with #136608 to make sure we don't re-introduce the crash in the future.