Update k8s example

[jsirianni]

Description of Changes

• Switched to kubernetes_container plugin
• Use stdout and kubectl logs to view stanza output, instead of file_output inside the container
• Use persistent storage for offset database
• Switch to latest rbac api

This example can run onMminikube with zero configuration.

Please check that the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• Add a changelog entry (for non-trivial bug fixes / features)
• CI passes

[djaglowski]

Log Files	Logs / Second	CPU Avg (%)	CPU Avg Δ (%)	Memory Avg (MB)	Memory Avg Δ (MB)
1	1000	1.4655333	+0.06897259	128.95204	+0.19908142
1	5000	5.155183	-0.17252064	139.2015	+1.8138428
1	10000	9.534603	-0.3796444	144.16487	-0.08552551
1	50000	46.4489	-0.43344498	173.8843	-2.3411865
1	100000	98.91476	+10.6117935	232.83783	+6.5176544
10	100	1.862072	+0.1379385	133.91891	+0.9352112
10	500	6.241338	+0.8964801	138.04836	-2.5196686
10	1000	11.707051	+0.9484129	146.1968	+0.4731903
10	5000	54.44919	+0.29341888	178.64238	+1.2901459
10	10000	97.93902	-9.587624	214.8226	-11.48114

[codecov]

Codecov Report

Merging #348 (d1f5733) into master (c254bee) will decrease coverage by 0.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #348      +/-   ##
==========================================
- Coverage   69.58%   69.45%   -0.12%     
==========================================
  Files         123      123              
  Lines        6495     6495              
==========================================
- Hits         4519     4511       -8     
- Misses       1494     1504      +10     
+ Partials      482      480       -2     

Impacted Files	Coverage Δ
operator/builtin/input/tcp/tcp.go	69.30% <0.00%> (-4.39%)	⬇️
operator/builtin/output/forward/forward.go	55.07% <0.00%> (-4.35%)	⬇️

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