docs: rename category filenames from Kubernetes to Cloud Native

[shmorri]

Prepare

• [x] Read PR guidelines
• [x] Read license information

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Description

Renamed most filenames from Kubernetes to Cloud Native to be more inclusive of different deployment methods.

Target issue

#2658

closes #2658

Implementation Details

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Test and Document the changes

• [x] Static code analysis has been run locally and issues have been fixed
• [x] Relevant unit and integration tests have been added/updated
• [x] Relevant documentation has been updated if any (i.e. user guides, installation and configuration guides, technical design docs etc)

[ossdhaval]

@shmorri

• I have added a commit that adds cloud-native tag to the documents
• Should admin/reference/kubernetes change to admin/reference/cloud-native as well?

[shmorri]

@ossdhaval Those reference files are Kubernetes-specific, so they definitely shouldn't change. I'm discussing the rest of it with Mohammad now.