chore: Remove additional div from Modal

[michaeldowseza]

Description

Additional div around the modal was initially used to associate the HTML node used by the Portal which would later be used to check from funnel step focus by checking if a focussed element is a descendant of this node. This information is useful to understand if a user is still on the same step when opening a modal from a form element in that given step, e.g. an s3 resource selector. However the additional div caused a layout shift.

We do not have a strong use case for embedded funnels inside a modal as they are primarily either a Form or Wizard and so we can ignore further interactions in this and change if new data is presented.

This change:

• Reverts/refactors some code made in 1494
• Adds a modal context so that funnel components can ignore some of the funnel functions when they detect they are in Modal

Related links, issue #, if available: AWSUI-22535

How has this been tested?

All existing unit tests passing which includes a test for if a funnel step state change happens when focus moves from an active step into a Modal inside a step.

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (7774a42) 94.17% compared to head (d29eccd) 94.17%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1635   +/-   ##
=======================================
  Coverage   94.17%   94.17%           
=======================================
  Files         649      650    +1     
  Lines       17510    17512    +2     
  Branches     5752     5753    +1     
=======================================
+ Hits        16490    16492    +2     
  Misses        951      951           
  Partials       69       69           

Files	Coverage Δ
src/container/internal.tsx	100.00% <100.00%> (ø)
...xpandable-section/expandable-section-container.tsx	100.00% <100.00%> (ø)
src/expandable-section/index.tsx	100.00% <100.00%> (ø)
src/expandable-section/internal.tsx	93.33% <ø> (ø)
src/internal/context/modal-context.ts	100.00% <100.00%> (ø)
src/modal/internal.tsx	100.00% <100.00%> (ø)
src/table/internal.tsx	99.28% <100.00%> (ø)

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