Bug_Fix: Property Recursion - Develop

[kbrunik]

Update cost property that was causing a recursion loop when accessed

This PR is based on PR #350 but cherry-picked to be able to be merged into develop instead of dev/refactor. PR #350 was an update to #345 based on reviewer feedback.

• Renamed property om_total_expense to om_total_expenses following naming convention in HybridSimulation.
• Updated type om_total_expense in the Outputs class and the om_total_expenses property to a Sequence.
• Changed cf_operating_expenses from a Numpy Array type to a Tuple to avoid additional errors when accessing the property.
• No recursion loop occurred when accessing the property after these updates.

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Impacted areas of the software

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PR #350 was approved by @dguittet.

Test results, if applicable