Migrate ServiceProviderRegistry upgrade tooling to `announceUpgradePlan`

[rjan90]

Context

PR #547 adds announceUpgradePlan(address,uint96) to ServiceProviderRegistry, but the existing operator helper, service_contracts/tools/service-provider-registry-announce-upgrade.sh, still exclusively generates the deprecated announcePlannedUpgrade((address,uint96)) call with an absolute AFTER_EPOCH.

The currently deployed registry implementations predate the new selector, so the first upgrade that introduces it must still be announced through the legacy interface. After that upgrade, registry announcements should use a relative delay so Safe signing time does not consume the requested notice window.

Scope

Bring the ServiceProviderRegistry operator flow in line with the FWSS dual-mode transition introduced in #547.

Acceptance criteria

• Add a delay-based mode that calls announceUpgradePlan(address,uint96) and accepts UPGRADE_DELAY_EPOCHS.
• Make delay mode the normal/default path once the deployed registry supports the selector.
• Preserve an explicit ANNOUNCEMENT_MODE=legacy bootstrap path using AFTER_EPOCH for:
  • the first upgrade from an implementation that predates announceUpgradePlan;
  • rollback to such an implementation while that rollback remains supported.
• Reject ambiguous configurations that set both delay and absolute-epoch inputs.
• Preflight-simulate the selected call from the proxy owner before producing calldata, so an unsupported selector, invalid implementation, or overflowing delay is caught before a Safe proposal is created.
• After execution, read back nextUpgrade(), verify the implementation and effective afterEpoch, and record the observed epoch as the source of truth.
• Update the tooling README/runbook to explain the per-network transition from legacy to delay mode.
• Document the cleanup condition: remove legacy mode after both deployed registries support the new selector and rollback to the older implementation is retired.
• Add or update tests/checks for both modes and their validation paths.

Sequencing note

Selector availability is determined by the implementation currently behind each network's registry proxy. Calibnet and Mainnet may therefore require different modes during the transition.