Consensus sign off on component level tests

[dnadales]

This issue enumerates the component level tests that need to pass to give the UTxO HD feature a green light for downstream integration.

• Re-enable the ThreadNet tests in the UTxO-HD feature branch #3998
• Cardano eras transitions tests #4043
• Create property tests for the BackingStore type that are implementation-agnostic #3954
• Property-test the mempool with ledger tables #4044
• Contracts on the instances of StowableLedgerTables, at least that unstow . stow= id, stow . unstow will overwrite the ledger tables #4270
• Contracts on the instances of TableStuff and TickedTableStuff (classes that will be renamed). with . project = id, properties on map and traversable like operations #4271
• ChainDB.getLedgerBackingStoreValueHandle. One fundamental property we want to check is that the backing store view remains invariant to operations in the legder. This test could be written using operations on the ledger DB, thus avoiding the need for adding tables to the test blocks used in the ChainDB tests (TODO create issue).
• Test LedgerDB.getLedgerTablesAtFor #4171
• ThreadNet: Use getLedgerBackingStoreValueHandle inside forkTxProducer #3950

[jorisdral]

The proposed ChainDB.getLedgerBackingStoreValueHandle test is subsumed by the model-based tests that are introduced in #3954. The model mocks value handles in such a way that they have a consistent view of the database state at the time the value handle is created. This view is invariant under operations to the backing store itself. If a BackingStore implementation were to create value handles that do not have this consistent view property, the tests will likely fail.