Automatic merge from submit-queue (batch tested with PRs 46734, 46810, 46759, 46259, 46771)

Improve code coverage for pkg/kubelet/images/image_gc_manager

**What this PR does / why we need it**:
#39559 #40780

code coverage from 74.5% to 77.4%

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

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```