[KV Connector] Remove compat support for pre-v0.12.0 constructor signatures without `KVCacheConfig` (#39832)
The v0.12.0 release contained initial support for HMA in KV Connectors. As part
of these changes, a KVCacheConfig argument was added to KV connector
constructors. Backwards compatibility support for out-of-tree connectors was
included in this change, with a very prominent warning. See #25712 and #27887.
Since the warning has been around for over 5 months, we can safely remove
the support of it.
Signed-off-by: yewentao256 <zhyanwentao@126.com>