Refactoring database_fixture.cpp to remove test case names.

[manikey123]

User Story Create a new fixture class that is derived from database_fixture, add a hook function there, every individual test case that uses that fixture can define their own parameters for initializing the app instance. Reference: https://github.com/bitshares/bitshares-core/pull/1903#discussion_r313486460 Impacts Describe which portion(s) of BitShares Core may be impacted by your request. Please tick at least one box.

• [ ] API (the application programming interface)
• [X] Build (the build process or something prior to compiled code)
• [ ] CLI (the command line wallet)
• [ ] Deployment (the deployment process after building such as Docker, Travis, etc.)
• [ ] DEX (the Decentralized EXchange, market engine, etc.)
• [ ] P2P (the peer-to-peer network for transaction/block propagation)
• [ ] Performance (system or user efficiency, etc.)
• [ ] Protocol (the blockchain logic, consensus, validation, etc.)
• [ ] Security (the security of system or user data, etc.)
• [ ] UX (the User Experience)
• [ ] Other (please add below)

Additional Context (optional) Add any other context about your request here.

CORE TEAM TASK LIST

• [ ] Evaluate / Prioritize Feature Request
• [ ] Refine User Stories / Requirements
• [ ] Define Test Cases
• [ ] Design / Develop Solution
• [ ] Perform QA/Testing
• [ ] Update Documentation

[manikey123]

@abitmore plz assign the issue to me