feat(metrics): Add new datasource to kumactl install metrics

[lahabana]

Summary

This adds the plugin to grafana and add a new panel in the mesh dashboard

Full changelog

• Update grafana to 8.1.2
• Download the plugin in an init container and set it up as a new datasource
• Add a panel in the new dashboard

Testing

• Unit tests
• Manual testing on Kubernetes

Backwards compatibility

• Add backport-to-stable label if the code is backwards compatible. Otherwise, list breaking changes.

[bartsmykla]

lgtm

[lahabana]

@Mergifyio update

[mergify]

Command update: success

Branch has been successfully updated

[codecov-commenter]

Codecov Report

Merging #2640 (5d32a44) into master (3665e51) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2640      +/-   ##
==========================================
+ Coverage   51.97%   52.00%   +0.03%     
==========================================
  Files         871      871              
  Lines       49512    49513       +1     
==========================================
+ Hits        25733    25750      +17     
+ Misses      21699    21682      -17     
- Partials     2080     2081       +1     

Impacted Files	Coverage Δ
...ctl/cmd/install/context/install_metrics_context.go	100.00% <100.00%> (ø)
api/observability/v1/mads.pb.go	35.56% <0.00%> (+1.03%)	⬆️
pkg/xds/generator/direct_access_proxy_generator.go	83.90% <0.00%> (+1.14%)	⬆️
pkg/mads/v1/client/client.go	43.75% <0.00%> (+2.50%)	⬆️
pkg/kds/client/sink.go	52.27% <0.00%> (+4.54%)	⬆️
pkg/core/bootstrap/autoconfig.go	54.46% <0.00%> (+8.03%)	⬆️

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