kvserver: maybeAddRangeInfoToResponse called frequently under sysbench (0.1% cpu)

Potentially on each request. I saw this take >3% on a blocking profile and it shows up on the CPU profile as well.

I ran `BenchmarkSysbench/SQL/3node/oltp_read_write-1` with `-test.benchtime=1000x` and it printed 520 times, i.e. around 52k invocations.

```
if rand.Intn(100) == 1 {
fmt.Fprintln(os.Stderr, "NOW")
}
```

This suggests that we have a caching problem, and this function isn't cheap.

Epic CRDB-55523
Jira issue: CRDB-44725