receiver/k8scluster: Use OTel conventions for metadata

[asuresh4]

Description: Updates to metadata.

• Update collected metadata to use OTel conventions
• Replaces kubernetes_service_ prefix on service name in Pod metadata with k8s.service.

Testing: Updated tests.

[codecov]

Codecov Report

Merging #2530 (9f79731) into main (d3f3d9b) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2530      +/-   ##
==========================================
+ Coverage   91.05%   91.06%   +0.01%     
==========================================
  Files         417      417              
  Lines       20935    20937       +2     
==========================================
+ Hits        19063    19067       +4     
+ Misses       1408     1407       -1     
+ Partials      464      463       -1     

Flag	Coverage Δ
integration	69.22% <ø> (ø)
unit	89.94% <100.00%> (+0.01%)	⬆️

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Impacted Files	Coverage Δ
receiver/k8sclusterreceiver/collection/metadata.go	100.00% <100.00%> (ø)
receiver/k8sclusterreceiver/collection/pods.go	94.11% <100.00%> (ø)
receiver/k8sclusterreceiver/watcher.go	97.64% <0.00%> (+2.35%)	⬆️

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