spfresh: add search diagnostic stats (#10)

## Summary
- add SPFreshSearchStats fields for read_only, effective oversample_factor, and per-request partition cache hits/misses
- regenerate Go protobuf and proto.lock

## Validation
- protolock status -lockdir=scripts -protoroot=proto
- go build ./go-tipb/...
- cargo check
- cargo check --no-default-features --features prost-codec

Co-authored-by: Lloyd-Pottiger <yan1579196623@gmail.com>
Reviewed-on: https://git.pingcap.net/pingkai/tipb/pulls/10
(cherry picked from commit ebb6356a3c319d7eb86275885232249b41920a81)

Author: Lloyd

go-tipb/spfresh_search.pb.go

@@ -70,4 +70,10 @@ message SPFreshSearchStats {
     // request.
     uint64 tikv_client_rpc_count = 10;
     uint64 tikv_client_rpc_micros = 11;
+    bool read_only = 12;
+    // Effective oversample factor used by the server for this request.
+    double oversample_factor = 13;
+    // Process-local partition cache stats for this request.
+    uint64 partition_cache_hits = 14;
+    uint64 partition_cache_misses = 15;
 }

proto/spfresh_search.proto

@@ -8124,6 +8124,26 @@
                 "id": 11,
                 "name": "tikv_client_rpc_micros",
                 "type": "uint64"
+              },
+              {
+                "id": 12,
+                "name": "read_only",
+                "type": "bool"
+              },
+              {
+                "id": 13,
+                "name": "oversample_factor",
+                "type": "double"
+              },
+              {
+                "id": 14,
+                "name": "partition_cache_hits",
+                "type": "uint64"
+              },
+              {
+                "id": 15,
+                "name": "partition_cache_misses",
+                "type": "uint64"
               }
             ]
           }