Logical Synchronizer Upgrades 76 Milestone 1: Core Primitives & Topology

Milestone 1: Core Primitives & Topology

| Estimated Delivery | Month 2 after announcement of approval of this proposal | | :---- | :---- | | Focus | Building the foundational data structures and topology transactions. |

Deliverables:

• Implementation of PhysicalSynchronizerId vs LogicalSynchronizerId distinction in the codebase.
• New Topology Transactions: LsuAnnouncement and SynchronizerKillSwitch.
• Implementation of the "Topology Freeze" logic on the sequencer.
• Ability to start a successor synchronizer with a genesis topology derived from an existing one (demonstrated via integration testing).

_Originally posted by @pedrodneves in https://github.com/canton-foundation/canton-dev-fund/issues/76#issuecomment-4306165684_