perf(files_external): Increase S3 cache caps

[joshtrichards]

Summary

Changes:

• objectCache: 512-->2048
• directoryCache: 512-->8192
• filesCache: 512-->4096

Impact:

• Better cache hit rate during large scans
• Fewer repeated S3 metadata requests
• Faster recursive scan/listing operations on large buckets

Note:

• Higher per-request memory usage in large-scan scenarios (still bounded by caps)
• Minimal impact on small requests that do not exceed current cache limits

TODO

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI