Add circuit breaker user guide

Kmesh supportted circuit breaker in Kernel-Native mode during the OSPP. But the circuit breaker user guide is still missing.

We need to add it.

Start by reviewing the existing website documentation structure and the circuit breaker support in Kernel-Native mode. Done means the missing circuit breaker user guide has been added with sufficient usage information for readers, but the issue does not name a file, test, or specific guide contents.

Written by the indexing model from the issue text.