docs: add VPC Egress Gateway BFD mitigation guide

[changluyi]

Summary

• Add bilingual Knowledge Solution documentation for VPC Egress Gateway BFD issues affecting ACP 4.3.0, 4.3.1, and 4.3.2.
• Recommend upgrading to ACP 4.3.3 or later; retain the manual configuration only as a temporary solution for clusters that cannot upgrade immediately.
• Explain why the existing health probe does not detect 0 sessions and provide a temporary liveness probe configuration.
• Document optional CPU and BFD interval mitigations using kubectl edit to preserve existing resource fields.

Verification

• English SHA256 matches the Chinese sourceSHA.
• Relative documentation links exist in both languages.
• Markdown whitespace checks pass and no kubectl patch commands remain.
• The previous PR build completed successfully; the updated commit will be validated by the new CI run.