fix(openapi): implement processInlineDuplicateFields to resolve duplicate JSON field names

[ash-thakur-rh]

Description

Fixes #7380

This PR adds a duplicate field detection processor to prevent "duplicate key in map literal" errors when embedded structs have conflicting JSON field names(cluster-api-provider-azure had conflicting JSON field name)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change
• Chore (non-breaking change which doesn't affect codebase;
  test, version modification, documentation, etc.)

Checklist

• Code contributed by me aligns with current project license: Apache 2.0
• I Added CHANGELOG entry regarding this change
• I have implemented unit tests to cover my changes
• I have added/updated the javadocs and other documentation accordingly
• No new bugs, code smells, etc. in SonarCloud report
• I tested my code in Kubernetes
• I tested my code in OpenShift

[manusa]

LGTM, thx!