Add a new `PyList::try_new` method

[messense]

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PyList::new requires a infallible iterator which is sometimes awkward to use.

Is this new API desirable?

[davidhewitt]

While I agree that our collection interfaces can definitely be made more user-friendly, I think we should take a bit of time to design something new before adding too many new functions.

I think this loosely combines well with the changes proposed in #1667 as something we can experiment with for 0.15, if you're ok with waiting for it for a bit?

[messense]

While I agree that our collection interfaces can definitely be made more user-friendly, I think we should take a bit of time to design something new before adding too many new functions.

I think this loosely combines well with the changes proposed in #1667 as something we can experiment with for 0.15, if you're ok with waiting for it for a bit?

No problem, it’s not blocking anything.