Generating cis3 signatures in test case

[DOBEN]

Purpose

Some of the test cases from cis3 haven't been migrated yet. Migrating some of them. In addition, add test cases that showcase how to generate account signatures within a test case (meaning how to create keypairs and how to use the signing function).

Changes

• Add test case test_inside_signature_permit_transfer
• Add test case test_outside_signature_permit_transfer
• Add test case test_inside_signature_permit_update_operator
• Add test case test_outside_signature_permit_update_operator

[DOBEN]

It's good that you added the tests, but as Ales also pointed out, it is not clear why the tests with generated keys also use the dummy constants. Please explain and/or fix that 

I added the following explanation:

    // The `viewMessageHash` function uses the same input parameter `PermitParam` as
    // the `permit` function. The `PermitParam` type includes a `signature` and
    // a `signer`. Becuase these two values (`signature` and `signer`) are not
    // read in the `viewMessageHash` function, any value can be used and we choose
    // to use `DUMMY_SIGNATURE` and `ALICE` in the test case below.