[ModalUnstyled] Apply aria-hidden to the correct Elements in the tree when disablePortal or container props are used

[Greg-NetDuma]

Before if someone used disablePortal or container and opened a modal the whole page became inaccessible to Screen Readers. This PR aims to fix that.

Changes:

• Make sure we pass in the correct container if disablePortal is used.
• If the modal container is deep in the tree we need to make sure every sibling in every ancestor level is aria-hidden and and every aria-hidden we added gets cleaned up properly on unmount.
• In addition because we don't differentiate between aria-hidden tags that got added by modals and added by devs, we need to pierce through (remove) every aria-hidden attribute in every ancestor of the modal container; this is to prevent no accessible elements on a page when multiple modals are present.

PS.: Existing tests were wrong, fixed them.

Problems I've discovered while fixing this:

• disableEnforceFocus is not respected by ModalManager, it should not apply aria-hidden to other elements then (in my opinion)
• TrapFocus sentinel elements should always be aria-hidden
• TrapFocus sentinel elements should have tabIndex={-1} when disableEnforceFocus is set to prevent people tabbing to them.

Known Problems:

• I only accounted for Modals that are either using disablePortal, container or using the default portal in body. Every other case will still break. I've not found a corner case like that yet.
• If aria-hidden states were changed outside of Modal while the Modal was up the change is not tracked (same as before this PR)

• I have followed (at least) the PR section of the contributing guide.

[mui-bot]

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@material-ui/core: parsed: +0.08% , gzip: +0.13%
@material-ui/unstyled: parsed: +0.33% , gzip: +0.43%
@mui/joy: parsed: +0.06% , gzip: +0.10%

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Generated by 🚫 dangerJS against 947cfa8

[Greg-NetDuma]

This clearly needs some new test cases, for example:

1. Modal added that doesn't use portal on after a Modal that uses the portal - toplevel is not aria-hidden
2. Modal added that doesn't use portal on after a Modal that doesn't use the portal - toplevel is still not aria-hidden
3. Modal added that uses portal on after a Modal that doesn't use the portal
4. Modal added that uses portal on after a Modal that uses the portal - previous behaviour

Technically I can get away just adding the 1. and 3. because the previous modal doesn't affect adding a new one on top of it.

Last Modal removed doesn't really need a test because it's a different codepath, aria-hidden is always removed.

I ended up fixing the existing tests because they were wrong.

[ZeeshanTamboli]

@Greg-NetDuma Can you merge with the latest master branch and fix the tests?

[ZeeshanTamboli]

Since there is no activity, I am closing this PR.