Merge pull request #48256 from xiangpengzhao/move-pkg-util

Automatic merge from submit-queue (batch tested with PRs 48481, 48256)

Refactor: pkg/util into sub-pkgs

**What this PR does / why we need it**:
- move code in pkg/util into sub-pkgs
- delete some unused funcs

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #15634

**Special notes for your reviewer**:
This is the final work of #15634. It will close that issue.
/cc @thockin 

**Release note**:

```release-note
NONE
```

hack/.golint_failures

@@ -431,7 +431,6 @@ pkg/security/podsecuritypolicy/user
 pkg/security/podsecuritypolicy/util
 pkg/securitycontext
 pkg/ssh
-pkg/util
 pkg/util/bandwidth
 pkg/util/config
 pkg/util/configz
@@ -439,6 +438,7 @@ pkg/util/dbus
 pkg/util/ebtables
 pkg/util/env
 pkg/util/exec
+pkg/util/file
 pkg/util/goroutinemap/exponentialbackoff
 pkg/util/initsystem
 pkg/util/ipconfig