feat(load): Add metrics + gun reliability

[rodrigombsoares]

Summary

First stacked PR for devenv load-test observability and gun reliability. Extracted from the e2e-load-prod-enablement monolith; still scoped to local devenv only.

Running existing load tests now prints per-phase timing breakdowns, failure counts, and a message ID summary at the end of each run. CCIPLoadGun uses sync.Cond single-flight concurrency so overlapping WASP calls wait instead of failing.

This PR also moves token minting on e2e tests to top level. To avoid holdings conflicts between tests leading to flakyness. Holding picking function is still sub-optimal, we need to harden that in follow up PRs.

Features

• LoadMetricsCollector (metrics.go) — records Send, Confirm Send, Confirm Exec, and Total durations per successful message; tracks phase failure counts (send / confirm send / confirm exec)
• Phase metrics output — PrintPhaseMetricsSummary logs Min/P90/P95/P99 per phase; bridges successful records to CCV MessageMetrics summary
• CCIPLoadGun reliability — sync.Cond-based single-flight (peak concurrency asserted ≤ 1); collects messageIDs after confirm-send (canton needs to run sequentially due to CIDs changing on every call)
• New gun API — LoadGunOptions with injectable ConfirmSendFunc and ConfirmExecTimeout (prod-testnet workaround wired in a later PR); devenv tests use cantonSourceConfirmSend / evmSourceConfirmSend
• runWASP enhancements — configurable CallTimeout via CANTON_LOAD_CALL_TIMEOUT; schedule logging; deferred message summary; metrics printed at end of run
• Canton send logging — impl.go logs messageID + seqNo after CCIP send parse

Testing

Requires a running local devenv and ccip/devenv/env-canton-evm-out.toml.

1. make start-devenv
2. make run-canton2evm-load
3. make run-evm2canton-load
4. make run-canton2evm-token-load
5. make run-evm2canton-token-load

[github-actions]

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