Fix swap memory permission and gracefully handle permission errors

[Snuffy2]

• Use different swap memory endpoint that works with current permissions
• Gracefully handle errors, especially permission errors and show this in the Error text
• Add more type hints and annotations

[alexdelprete]

While you're preparing this, could you check this line? the memory variable looks undefined (it's defined in the line after)

[alexdelprete]

You went back to pfstates vs pf_states?

[Snuffy2]

You went back to pfstates vs pf_states?

Yes, for testing the errors. Not final.

[alexdelprete]

Looks good, I'll merge it.