fix: issue where KeyfileAccount would not stay unlocked [APE-1586]

[antazoey]

What I did

In ape-safe, I was prompted "Leave unlocked?" over and over again and it was because signers were re-checked and reloaded and thus lost the "yes" to my prompt... So it is would be nice if Ape remembered I said "yes" to leave the account unlocked.

How I did it

Only create the KeyfileAccount class once.

How to verify it

see second test. The first one was me trying to figure out but is still a nice test

Checklist

• All changes are completed
• New test cases have been added
• Documentation has been updated

[antazoey]

I guess one may want it to be relocked on when calling load() again? in which case, the caching can happen at the ape-safe level.
But it is just prone to be a problem again in future applications...

There is .lock() method you can and should call anyway.. to relock the account... It was just frustrating to have always bash "yes, leave unlocked" and it is just never stayed unlocked-

[antazoey]

was approved before, all i did was make tests happy since