Improved Agent mode capabilities

[Col-E]

In agent mode:

• Allow users to dump thread stacktraces in a clean UI (Exportable as text)
  • Can jump to class/methods as defined in the trace
• Visualize analytics using the manager beans
• Intercept shutdown events and lock it until the user closes Recaf, not the target application
  • Prevent program being analyzed from closing
  • As for standard application closes (main method finishes) this may be impossible to intercept unless we're a startup agent (because then we can rewrite all main methods to include hooks)

Seeing that in 4x the agent capability is facilitated via https://github.com/Col-E/InstrumentationServer the necessary work for this will actually be done over there. Recaf will just send the appropriate data to request this info.

The beans are already queried in the new attach window.