Improvements to the Portal to ISAbelle repository

[albertqjiang]

• [x] Solve memory leak issues
• [x] Match jEdit Sledgehammer performance
• [x] Upgrade to Isabelle2022
• [x] Implement functions that help conjecturing and premise selection
• [x] Serialise and reload top level state objects (can't be done)

[albertqjiang]

isabelle 2022 works, except for the sledgehammer component. will update when the problem is fixed