fix: default call transactions would not get prepared when sender is a contract

[antazoey]

What I did

it is difficult to test this without a provider that can handle impersonated accounts (can't wait for boa to be part of ape core).
but if your account is a contract and you call a fallback method on another contract, the transaction would never get prepared causing you to have to manually specify nonce= and everything else you neeed.

How I did it

• move prepare_transaction() to BaseAddress class.
• if the given sender isnt an account but is base-address, still do the prepare_transaction() part.

How to verify it

I had to add exception kwarg to SignatureError so i can at least verify the txn data is now populated.
I also confirmed with breakpoint and it unblocks me someplace else too. added a test.

Checklist

• All changes are completed
• Change is covered in tests
• Documentation is complete