Ingest stats panic - fix (#1440)

Fixes not protected concurrent map access.

```
fatal error: concurrent map read and map write

goroutine 193 [running]:
internal/runtime/maps.fatal({0xa2c93c?, 0x0?})
        /usr/local/go/src/runtime/panic.go:1058 +0x20
github.com/QuesmaOrg/quesma/platform/stats.(*Statistics).Process(0x1279838?, 0x9f?, {0x400e74199f?, 0x22?}, 0x1d?, {0xa09a4e?, 0x2b?})
        /platform/stats/ingest_statistics.go:127 +0x60
github.com/QuesmaOrg/quesma/platform/functionality/bulk.sendToClickhouse({0xc02f78, 0x4015dda210}, 0x0?, {0xf920c5f2d4b8, 0x40001ea408}, 0x1, 0x4000323400)
        /platform/functionality/bulk/bulk.go:274 +0x18c
```

Author: nablaone

platform/stats/ingest_statistics.go

@@ -83,9 +83,6 @@ func (s *Statistics) process(index string,
 
 	flatJson := util.FlattenMap(jsonData, nestedSeparator)
 
-	mu.Lock()
-	defer mu.Unlock()
-
 	statistics, ok := (*s)[index]
 	if !ok {
 		statistics = &IngestStatistics{IndexName: index, Keys: make(map[string]*KeyStatistics)}
@@ -121,6 +118,10 @@ func (s *Statistics) process(index string,
 }
 
 func (s *Statistics) Process(ingestStatsEnabled bool, index string, jsonData types.JSON, nestedSeparator string) {
+
+	mu.Lock()
+	defer mu.Unlock()
+
 	if ingestStatsEnabled {
 		s.process(index, jsonData, false, nestedSeparator)
 	}
@@ -130,6 +131,10 @@ func (s *Statistics) Process(ingestStatsEnabled bool, index string, jsonData typ
 }
 
 func (s *Statistics) UpdateNonSchemaValues(ingestStatsEnabled bool, index string, jsonData types.JSON, nestedSeparator string) {
+
+	mu.Lock()
+	defer mu.Unlock()
+
 	if ingestStatsEnabled {
 		s.process(index, jsonData, true, nestedSeparator)
 	}