NNS1-3281: Decode TVL state from stable memory

[dskloetd]

Motivation

This is the follow-up to #5431
In that PR we stored the TVL state to stable memory but we couldn't yet restore the TVL state from stable memory because we didn't have a release that made sure there was TVL state to be restored from stable memory.

After the most recent upgrade we now do so we can complete the TODOs left in that PR.

Changes

1. Load TVL state from stable memory.
2. Decode loaded TVL state into canister state.

Tests

1. Remove test that checks TVL state is not decoded.
2. Update test to make sure that TVL state is decoded.

Todos

• Add entry to changelog (if necessary).
  covered