fix(issuance): fix test configuration to resolve CI failure

- Update test script to use main hardhat config instead of test-specific config
- Remove unused test/hardhat.config.ts file
- Fixes OpenZeppelin upgrades plugin contract resolution issue
- All 40 RewardsEligibilityOracle tests now pass

Resolves issue introduced in 39b161c where test config couldn't properly
resolve contract sources for OpenZeppelin upgrades plugin validation.

Author: RembrandtK

packages/issuance/test/hardhat.config.ts

@@ -49,7 +49,7 @@
     "generate:interfaces": "node scripts/generateInterfaceIds.js --silent",
     "clean": "rm -rf build",
     "test": "pnpm build && pnpm test:self",
-    "test:self": "hardhat test tests/*.test.ts tests/**/*.test.ts",
+    "test:self": "cd .. && hardhat test test/tests/*.test.ts test/tests/**/*.test.ts",
     "test:coverage": "pnpm build && pnpm test:coverage:self",
     "test:coverage:self": "scripts/coverage",
     "lint": "pnpm lint:ts; pnpm lint:json",