[Tooling][Savepoints/Rollbacks] Integrate Snapshots and Rollbacks with RPC

[deblasis]

Objective

Replace the no-op / faked code in handlers.go with the real functionality that has been developed in "Work stream A" as defined in #562

Origin Document

#493 and #562

Goals

• Have real snapshotting in place triggerable by the CLI via RPC
• Have real rollbacks in place triggerable by the CLI via RPC

Deliverable

• A PR with implementation tending to the goals above
• E2E tests (or documentation) that verify rollbacks triggered via the CLI

Non-goals / Non-deliverables

• Exhaustive testing of every snapshot / rollback usecase

General issue deliverables

• Update the appropriate CHANGELOG(s)
• Update any relevant local/global README(s)
• Update relevant source code tree explanations
• Add or update any relevant or supporting mermaid diagrams

Testing Methodology

• New tests: Documentation on how to use/verify this
• All tests: make test_all
• LocalNet: verify a LocalNet is still functioning correctly by following the instructions at docs/development/README.md

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Creator: @deblasis
Co-Owners: @Olshansk