Add support for ternary conditional expression in tail call optimization

[kiendang]

This PR enables tail call optimization for ternary conditional expression in return statement.
e.g

@tco
def tail_sum(x, acc=0):
    return acc if len(x) == 0 else tail_sum(x[1:], acc + x[0])

[azazel75]

@kiendang thanks for the contribution, can you please add a test for this?.

[kiendang]

I already did?

[kiendang]

Sorry please don't merge yet. It's not perfect. I'll update + add more tests soon.

[kiendang]

@azazel75 I've finished. Please review when you have time.

@tco
def tail_sum(x, acc=0):
    return acc if len(x) == 0 else tail_sum(x[1:], acc + x[0])

will now expand to

return (acc if len(x) == 0 else (TCOType.CALL, tail_sum, [x[1:], acc + x[0]], {}))

I also added support for non-return ternary expression in tail position and added more tests (basically all the existing tests for tco rewritten using ternary expression).