Move "array_editor" to "StandardEditors" contributed examples

[aaronayres35]

closes #1646

This PR takes the example array_eitor.py which used to sit in the documentation and moves it into the traitsui/examples/demo/Standard_Editors module. It also generates a new screenshot for the example and then uses these in the documentation. It removes the old screenshot and example file.

Checklist

• Add a news fragment if this PR is news-worthy for end users. (see docs/releases/README.rst)

[rahulporuri]

It looks like there are a couple of bugs here.

• the separators between the different sections of the UI seem off. They look off in the image and they look off locally when i run the example.
• the integer sections of the editor used to show 0 earlier but now they show 0.0.

[aaronayres35]

It looks like there are a couple of bugs here.

• the separators between the different sections of the UI seem off. They look off in the image and they look off locally when i run the example.
• the integer sections of the editor used to show 0 earlier but now they show 0.0.

Yeah very true, it doesn't look right. I believe these are separate issues / bugs from the changes here. I will open separate issues / PRs to address them.
ref:
for 2nd bullet #1694

I recall seeing other issues with the separators not lining up correctly... I will see if I can find the other issue.
EDIT: #1312 (doesn't appear to be the same issue, but related)
also relevant code I believe is what we touched in #1549

[aaronayres35]

Once #1702 is merged I will regenerate the screenshots and this PR should be good to go

[rahulporuri]

@aaronayres35 i'm still not conviced about #1702 but I don't want this PR stuck in limbo.

Can you do some git magic locally to generate a screenshot without the separator issue - and push that screenshot on this branch? That way, we can push this PR ahead without being blocked on #1702 .

[aaronayres35]

@aaronayres35 i'm still not conviced about #1702 but I don't want this PR stuck in limbo.

Can you do some git magic locally to generate a screenshot without the separator issue - and push that screenshot on this branch? That way, we can push this PR ahead without being blocked on #1702 .

That makes sense to me. TBH I am a little unsure on 1702 still myself. I don't really understand how previously things all looked correct for me locally, and now there was an off by one error (I think change occurred after updating macOS, but that doesn't mean change is correct as it might break code for older macOS?)
I've regenerated the correct looking screenshot on this PR and added a news fragment. This look okay @rahulporuri

[rahulporuri]

LGTM 🎉 Thanks for the changes!