min start ts of `initStatsCtx` is not tracked

[you06]

Bug Report

Please answer these questions before submitting your issue. Thanks!

tidb/pkg/session/session.go

Lines 3510 to 3514 in 2300ac6

	// setup init stats loader
	initStatsCtx, err := createSession(store)
	if err != nil {
	return nil, err
	}

The min start ts will block gc to guarantee the ongoing transaction can see its data, but the min start ts of initStatsCtx is not tracked.

1. Minimal reproduce step (Required)

Inject 30min sleep when loading stats in init context.

See commit.

2. What did you expect to see? (Required)

Stats loaded after 30min.

3. What did you see instead (Required)

[2024/05/27 21:08:25.631 +09:00] [ERROR] [domain.go:2314] ["init stats info failed"] [lite=true] ["take time"=30m0.002233833s] [error="[tikv:9006]GC life time is shorter than transaction duration, transaction starts at 2024-05-27 20:38:25.628 +0900 JST, GC safe point is 2024-05-27 20:49:25.682 +0900 JST"]

4. What is your TiDB version? (Required)

f5ac93e