feat: public data tree overrides for simulation (core)

[dbanks12]

Summary

Implements the first half of the public data tree overrides at simulation time plan.

• Adds PublicDataTreeOverride type and PublicDataTreeOverrideSchema to @aztec/stdlib/interfaces/client
• Adds applyPublicDataOverrides helper that injects overrides into the ephemeral world-state fork via sequentialInsert, matching the simulator's real write path
• Extends AztecNode.simulatePublicCalls with an optional publicDataOverrides parameter (backward compatible)
• Wires the helper into AztecNodeService.simulatePublicCalls between fork creation and processor construction
• Unit tests cover: empty/undefined input, single override, multiple overrides, and duplicate slot semantics

Overrides are injected only into the ephemeral fork and never reach block production.

Stacked on

merge-train/fairies

Test plan

• Unit tests for applyPublicDataOverrides in public_data_overrides.test.ts (5 tests, all passing)
• End-to-end coverage added in the follow-on PR (feat: public data tree overrides for simulation #22830)

[dbanks12]

• feat(aztec.js): cheatcode helpers for contract overrides #22899
• feat: contract class/instance overrides for simulation #22833
• feat: public data tree overrides for simulation #22830
• feat: public data tree overrides for simulation (core) #22829 👈 (View in Graphite)
• merge-train/fairies

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[dbanks12]

Collapsing into #22830 — the second stacked PR was meant for contract class/instance overrides (appendix), not this plumbing layer.