Deprecate use of DAST_API_SPECIFICATION and adopt DAST_API_OPENAPI

Deprecate use of DAST_API_SPECIFICATION and adopt DAST_API_OPENAPI

• Keeping variables the same between API Fuzzing and DAST...
  • Keeps logic in scanner simpler
  • Documentation sharing is easier
  • Easier on users configuring both DAST API and API Fuzzing
• Less ambiguity