Add managed by metric

[rubenvp8510]

Signed-off-by: Ruben Vargas [email protected]

Which problem is this PR solving?

• This PR adds a metric that reports which instances are managed by other tools, like maistra/istio.

[codecov]

Codecov Report

Merging #1831 (613247a) into main (6d5362f) will decrease coverage by 0.01%.
The diff coverage is 81.81%.

@@            Coverage Diff             @@
##             main    #1831      +/-   ##
==========================================
- Coverage   88.19%   88.18%   -0.02%     
==========================================
  Files         101      101              
  Lines        6142     6153      +11     
==========================================
+ Hits         5417     5426       +9     
- Misses        543      544       +1     
- Partials      182      183       +1     

Impacted Files	Coverage Δ
pkg/metrics/instances.go	88.57% <81.81%> (-0.80%)	⬇️

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[pavolloffay]

Did you try if maistra operator sets the managed-by?

[rubenvp8510]

Did you try if maistra operator sets the managed-by?

Yes I did.