smb: client: add tracepoints for deferred handle caching

smb: client: add tracepoints for deferred handle caching

Add tracepoints to observe handle caching behavior.

smb3_open_cached: emitted when an open reuses a cached handle from
a previous deferred close, avoiding a network round-trip

smb3_close_cached: emitted when a close is deferred (handle cached
for potential reuse by subsequent opens)

Signed-off-by: Bharath SM <bharathsm@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>