Add Istio plugin

[axdotl]

• I added a CHANGELOG entry for this change.
• I adjusted the corresponding documentation for this change.
• I adjusted the values.yaml file and the documentation for all values.

[codecov-commenter]

Codecov Report

Merging #342 (911f9cd) into rework-kobs-architecture (8a0abd4) will decrease coverage by 3.34%.
The diff coverage is 7.77%.

@@                     Coverage Diff                      @@
##           rework-kobs-architecture     #342      +/-   ##
============================================================
- Coverage                     46.43%   43.08%   -3.35%     
============================================================
  Files                            98      100       +2     
  Lines                          6803     7485     +682     
============================================================
+ Hits                           3159     3225      +66     
- Misses                         3577     4187     +610     
- Partials                         67       73       +6     

Impacted Files	Coverage Δ
plugins/plugin-istio/pkg/instance/instance.go	5.79% <5.79%> (ø)
plugins/plugin-istio/cmd/istio.go	9.79% <9.79%> (ø)
plugins/plugin-prometheus/pkg/instance/instance.go	5.72% <0.00%> (+5.72%)	⬆️

---

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 8a0abd4...911f9cd. Read the comment docs.