adding test to checks for duplicated parameters in defaults.yaml

[VGPReys]

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Closes #911 and #912

Adding runtime checks to:

• [x] evaluate duplicated parameters in default.yaml files.
• [x] validate default.yaml parameter schemes

Adding tests to:

• [x] evaluate duplicated parameters in default.yaml files.
• [x] validate default.yaml parameter schemes
• [x] test new validation functions