[docs] Add table-level active incremental warm-up guide

[bobhan1]

Summary

apache/doris#63832

• Update the read/write separation File Cache warm-up guide in both English and Chinese with table-level event-driven warm-up usage.
• Document ON TABLES syntax, INCLUDE/EXCLUDE matching rules, examples, refresh behavior, SHOW WARM UP JOB fields, detailed SyncStats JSON, BE Bvar metrics, and FE Prometheus metrics.
• Clarify that compute-group-level load-event warm-up and table-level ON TABLES load-event warm-up should not be configured together for the same source and destination compute groups.

Validation

• git diff --check
• Front matter JSON parsing and Markdown code-fence/admonition pairing check

Note: Docusaurus/docs-governance checks were not run because this checkout does not have node_modules; the docs governance scripts fail on missing gray-matter.