[EuiFlyout] Add a "push" instead of "overlay" option

[cchaos]

Kibana Maps and Canvas use this method but have to re-create the inner components of the flyout in order to achieve this. We should be able to handle this on the EUI side as a simple prop.

https://d.pr/free/i/U5EqIt

[cchaos]

Also should we allow attaching the flyout to particular wrappers? For example, getting details on a table row could have the flyout push right from the table instead of taking over the entire body:

Source: https://dribbble.com/shots/6559902-Untill-hospitality-management-platform-Reports/attachments

[snide]

Do you think think we'd instead do some sort of inset shadow or borders on these when they are pushovers? The one problem I have with the usage in maps is that split is super harsh.

[ryankeairns]

I've gone back-and-forth a bit with clearly defining the side panels in Canvas and I sense we need to also delineate the top section as well. Further, I have plans to move the page manager at some point as well. Point being, I wonder if we might need a separate component altogether, or perhaps as part of the Page layout component. Something that has a tinted/shaded background and can be fixed (top, bottom, left, right) and can contain any content (panels, accordions, plain text, etc.).

This may be a separate issue, but it jogged my mind :)

[cchaos]

I'm thinking that this may actually get solved with using the EuiResizablePanel and the toggle work happening in #3978

[github-actions]

👋 Hey there. This issue hasn't had any activity for 180 days. We'll automatically close it if that trend continues for another week. If you feel this issue is still valid and needs attention please let us know with a comment.

[cchaos]

Adding this to long-term goals, as I still think it could be a neat solution.

[cchaos]

Added in #4713, though it's technically still "fixed" position and can't be "contained" within a component. Gonna close it out.