[compatible] Add parameter to stop the chain after given slot

[joaosreis]

This PR introduces an optional parameter to the CLI (slot-tx-end), that defines the slot after which the node should reject new transactions and stop including any in blocks (in case the node is a BP). This functionality is part of the hard fork mechanism.

Summary of changes:

• Add optional slot-tx-end parameter to CLI.
• BP always uses an empty set of transactions to produce blocks after the slot-tx-end slot instead of fetching them from the transaction pool.
• The RPC function for sending user commands rejects commands after the slot-tx-end slot.
• The node doesn't try to add incoming transactions to the network pool after the slot-tx-end slot.
• The transaction pool drops all transactions when the slot-tx-end slot is reached.

Some unit tests (specifically, for the transaction pool) were added. The complete set of expected behaviors was demonstrated in a sandbox network.

[joaosreis]

!ci-build-me

[mitschabaude]

product approval without review

[joaosreis]

Closed in favor of #14516