`assert!` error messsage shows the source code under miden-debug `Executor`

[greenhat]

Add a test that puts assert! somewhere in the middle of the program (fibonacci or collatz) and check that the error message contains the correct source code extract pointing to the line with assert!.

[greenhat]

@djolertrk I cannot assign you to this issue, but this is the one we discussed on the call.

[greenhat]

#806 (comment) belongs here

[greenhat]

When 0xMiden/miden-debug#5 is merged we should add another test that checks the error message for source code.

[djolertrk]

When 0xMiden/miden-debug#5 is merged we should add another test that checks the error message for source code.

#849