fix(tsdb): Disable series id set cache size by default.

This commit changes `DefaultSeriesIDSetCacheSize` to zero so that the
tag value cache is disabled by default. There is a rare known bug where
the cache can cause a segfault which crasheds the process. The cache
is being disabled instead of removed as some users may still need the
cache for performance reasons.

tsdb/config.go

@@ -68,7 +68,8 @@ const (
 	DefaultMaxIndexLogFileSize = 1 * 1024 * 1024 // 1MB
 
 	// DefaultSeriesIDSetCacheSize is the default number of series ID sets to cache in the TSI index.
-	DefaultSeriesIDSetCacheSize = 100
+	// It is disabled by default.
+	DefaultSeriesIDSetCacheSize = 0
 
 	// DefaultSeriesFileMaxConcurrentSnapshotCompactions is the maximum number of concurrent series
 	// partition snapshot compactions that can run at one time.