backport: add delete verb for secrets (#3570)

[ksubrmnn]

Description:
Cherry-picks 8d0ec91 for v0.9.1,
required for garbage collection to work on OpenShift.

Affected area:

Functional Area
New Functionality	[ ]
Documentation	[ ]
Install	[X]
CLI Tool	[ ]
Certificate Management	[ ]
Control Plane	[ ]
Ingress	[ ]
Egress	[ ]
Networking	[ ]
Observability	[ ]
SMI Policy	[ ]
Sidecar Injection	[ ]
Security	[ ]
Upgrade	[ ]
Tests	[ ]
CI System	[ ]
Demo	[X]
Performance	[ ]
Other	[ ]

Please answer the following questions with yes/no.

1. Does this change contain code from or inspired by another project?
   • Did you notify the maintainers and provide attribution?
     No
2. Is this a breaking change?
   No

[codecov-commenter]

Codecov Report

Merging #3633 (1ae8df3) into release-v0.9 (865c66e) will not change coverage.
The diff coverage is n/a.

@@              Coverage Diff              @@
##           release-v0.9    #3633   +/-   ##
=============================================
  Coverage         66.59%   66.59%           
=============================================
  Files               169      169           
  Lines              7904     7904           
=============================================
  Hits               5264     5264           
  Misses             2609     2609           
  Partials             31       31           

Flag	Coverage Δ
unittests	66.59% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 865c66e...1ae8df3. Read the comment docs.