Add `call_internal` cheatcode

[MaksymilianDemitraszek]

To let users call internal methods of contracts

[kasperski95]

Is this cheatcode really needed? A user should be able to test internal functions with "pure Cairo" test runner.

[MaksymilianDemitraszek]

@kasperski95 User will not be able to test internal logic which may involve storage modifications. I think it is needed, although it has low priority. I will move it to improvements milestone.

[kasperski95]

A user could use impureim sandwich. Pure functions could be tested with pure Cairo and storage modifications could be tested with Cheatable Starknet fixture.

[MaksymilianDemitraszek]

@kasperski95 Definiatelty, but it kinda forces users to use certain pattern, don't you think it would be nice to have to give users the flexibility?

[Arcticae]

Discussed internally with @MaksymilianDemitraszek, postponing this one for after-1.0 release, since users might not need it.