Cache rarely-changing allowance-related DB objects

[matthew-li]

Description

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• Cached an instance of ComputingAllowanceInterface under the key "computing_allowance_interface" during the new project request form to avoid many redundant database lookups of the same objects.
• Updated new project request forms to take an already-instantiated instance of the class instead of creating a new one.

Type of change

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• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

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TODO.

PR Self Evaluation

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• My code follows the agreed upon best practices
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