bpo-37271: Optimize bytecode multiple times until it cannot be optimized further

[pablogsal]

https://bugs.python.org/issue37271

[nedbat]

@pablogsal Any chance you want to help get #13600 finished?

[pablogsal]

@nedbat Sure, I will talk with Victor to see if we can push it forward.

[pablogsal]

@serhiy-storchaka What do you think about this approach?

[pablogsal]

I have rebased and address the feedback. Also, I have added a max cap of iterations (although is not needed, it can be proven that the while loop will always finish) to make sure the time expended in the loop is always bounded.

[markshannon]

Looks good in general, just a couple of questions.

[pablogsal]

@markshannon I have added some comments as requested, check if they look good to you :)

[pablogsal]

CC: @Yhg1s

[pablogsal]

This is the code that is failing the assert currently:

def f(cond1, cond2):
    while 1:
        return 3
    while 1:
        return 5
    return 6

[Yhg1s]

GH-15970 should fix the lnotab issue.