Allow copy/paste from the echidna UI output

[0xicingdeath]

Describe the desired feature

The only way to currently get the assertion failures/call sequences from the UI is to screenshot it (before exiting). It would be really useful to be able to copy the calltrace, the same way we can do in text mode.

[rappie]

+1

This would be really convenient to add if it's not too much work :slightly_smiling_face:

However, you can exit out of Echidna and easily copy/paste it from the results that are printed in the terminal.