Post Types: Add 'at_a_glance' property and update dashboard widget logic. Refresh: 45035.diff

[SirLouen]

Following the patch in 45035.diff by @gwelser, I have refreshed and updated to work.

Testing Instructions

1. Add a new CPT
2. Set the at_a_glance argument to true in that CPT
3. Create a couple posts in that CPT, some published some not published
4. Go to the admin dashboard, and check if "At a Glance" show the right number of published posts

Trac ticket: https://core.trac.wordpress.org/ticket/45035

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[github-actions]

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Props sirlouen, westonruter, mukesh27, pbiron.

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[pbiron]

PR seems to work.

Have added 1 comment regarding the need to add at_a_glance arg to the hash in the register_post_type() DocBlock.

[github-actions]

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[pbiron]

The other thing this PR should do is output relevant CSS that uses the menu_icon param to register_post_type() for the icon in the At a Glance item. Have to think a bit about the best way to do that, especially to for menu_icon being an inline SVG.