Refactor out common code into a IndexItem::new constructor

[yotamofek]

#149404

[yotamofek]

@lolbinarycat Felt like doing something semi-mechanical that doesn't require too much concentration, so thought I'd tackle the issue you opened.

But TBH, after pulling out the common code into an IndexItem constructor, I'm not sure it makes much sense and/or is worth it.
What do you think?

[lolbinarycat]

It was working on #149460 that inspired this issue, and I agree that perhaps a substruct would be a better approach.

[yotamofek]

What do you think about how it looks now? @lolbinarycat
(still need to find a better name for the "sub struct")

[yotamofek]

the amount of times I typed "sub stract" instead of "sub struct"....... 😤

[lolbinarycat]

IndexItemInfo maybe? then the field could just be named info

[rustbot]

r? @GuillaumeGomez

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[yotamofek]

Well, done, not sure it's an improvement, but let's see what others think.

[GuillaumeGomez]

Changes look good to me. So if it's ok with lolbinarycat and notriddle, you can r=us.