fix: replace printStackTrace with RecordLog in ConfigUtil

Problem

ConfigUtil.java uses e.printStackTrace() in 3 places (lines 80, 107, 122) for error handling, which bypasses Sentinel's logging framework (RecordLog).

Impact

• Stack traces go directly to stderr instead of through the configured logging system
• Cannot control log level, format, or output destination for these errors
• Inconsistent with the rest of the codebase which uses RecordLog

Fix

Replace all 3 occurrences of e.printStackTrace() with RecordLog.warn() calls that include contextual information (file name or URL being loaded).

Local environment limitations, relying on CI/CD automated testing.