serviceability: rename NewInterface to Interface and old enum to InterfaceDeprecated

[elitegreg]

Summary

• Final cross-cutting step in the forward-compatible Device interfaces refactor — closes #3663. Design: gist.
• Pure rename: the legacy enum Interface → InterfaceDeprecated, the new struct NewInterface → Interface, the Device::new_interfaces field → Device::interfaces, and the legacy Device::interfaces field → Device::deprecated_interfaces. Equivalent rename across the Go, Python, and TypeScript serviceability SDKs.
• No on-disk format change. Borsh is positional, so the regenerated sdk/serviceability/testdata/fixtures/device.bin is byte-identical to the committed one.

Notes for reviewers

• The activator/ crate was deleted from the workspace in an earlier change, so the issue's "activator (minimal touch)" bullet is a no-op here.
• Device::find_interface_legacy is now unused — kept for this rename per the "pure rename" scope, separate cleanup follow-up.
• This PR is large (~70 files) but mechanical. Splitting along Rust ↔ SDK lines is possible if reviewers prefer; happy to do that on request.
• One small JSON-shape adjustment in the Go SDK: added json:\",omitempty\" to Device.DeprecatedInterfaces so it doesn't surface as a null field when callers populate only the new vec. The original Go SDK had omitempty on the new (formerly NewInterfaces) field; this PR keeps that behavior on the new canonical field and extends it to the deprecated slot for symmetry. JSON consumers that previously read Interfaces (legacy) now read either Interfaces (canonical) or DeprecatedInterfaces depending on which form they want.

Testing Verification

• make rust-fmt, make rust-lint, and cargo test --workspace --exclude doublezero-geolocation all pass. (The geolocation test compile failure on this branch reproduces on origin/main; pre-existing, unrelated.)
• make generate-fixtures confirmed device.bin is byte-identical pre/post rename.
• Python (uv run pytest) and TypeScript (bun test) SDK suites: 119 + 142 tests passing respectively.
• Go SDK tests pass (go test ./smartcontract/sdk/go/...).
• Manual sanity sweep: grep -r "NewInterface\b\|new_interfaces\b\|newInterfaces\b" returns only generated openconfig types and an unrelated controlplane NewInterface Go constructor — no remaining references in the doublezero serviceability surface.