### What this PR does / why we need it?
ucm_connector add has `has_connector_metadata` interface to adapt to the
latest KV connector in vLLM.
### Does this PR introduce _any_ user-facing change?
this PR doesn't introduce _any_ user-facing change.
### How was this patch tested?
- vLLM version: v0.14.0
- vLLM main:
d68209402d
Signed-off-by: UnifiedCacheManager <unifiedcachem@163.com>