Automatic merge from submit-queue (batch tested with PRs 61389, 66817, 66903, 66675, 66965). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Scalability tests: Increase sample size for pod startup latency measurement

**What this PR does / why we need it**:
This PR adds a way to increase a sample size used in pod startup latency measurement. We found that this phase is flaky and want to check if increasing a number of samples will help reducing a flakiness.


**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```