[backport/1.4] core: Use ISO 8601 UTC timestamps for logs

[joaoantoniocardoso]

Backport of #4124 (c1e2190) into 1.4 + log filename fix for consistency.

• tested.

[github-actions]

Automated PR Review

0. Summary

• Verdict: LGTM

Backports the ISO 8601 UTC log timestamp change from master (#4124 / c1e2190) into 1.4-dev: adds ISO8601_LOG_FORMAT and applies it to both the stderr and file loguru sinks in commonwealth/utils/logs.py, switches get_new_log_path to a UTC basic-format timestamp (%Y%m%dT%H%M%SZ), and aligns the run-service.sh and log_zipper timestamps to UTC ISO 8601. The extra "log filename fix for consistency" (UTC + basic ISO format on the log filename) is a sensible companion to the format change and is documented inline with a why comment.

Spot-checks:

• {time:YYYY-MM-DDTHH:mm:ss.SSS!UTC}Z — loguru's !UTC conversion + explicit Z suffix correctly emits UTC ISO 8601 with millisecond precision (MM = month, mm = minute, per Pendulum tokens).
• init_logger calls logger.remove() before re-adding sinks, matching the master version; stderr is added before the file sink so a failure in get_new_log_path still leaves stderr logging functional.
• run-service.sh uses date -u '+%Y-%m-%dT%H:%M:%SZ' — matches master byte-for-byte for the equivalent line.
• log_zipper/main.py uses time.strftime("%Y%m%dT%H%M%SZ", time.gmtime()) — correctly gives UTC (gmtime rather than localtime).
• import sys placement is alphabetically correct relative to import logging under isort's grouping.

No further comments, nice job 👍

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