[SSF-148] - Backend admin stats

[dburkhart07]

ℹ️ Issue

Closes #148

📝 Description

• Added an endpoint to get all stats by pantry
• Added query parameters to the above endpoints to filter by pantry names, selected years that orders were created, and pagination (each page is 10 pantries, so page 1 gets the first 10 pantries in the db, page 2 gets the 11-20th pantries)
• Added an endpoint to get the total stats for all pantries combined
• Added query parameters to the above endpoint to filter by the years that orders were created for the pantries
• Wrote pantry controller and service tests for the above endpoints, as well as every other endpoint in the pantries
• Removed totalItem, totalOz, and totalEstimatedValue from the donations entity
• Cleaned up unused code in other files

✔️ Verification

Tested endpoints, and made sure all tests passed

[amywng]

small nits but i trust so approving

[Yurika-Kan]

tested via postman

looks so great, found a possible bug