fix: Prevent breadcrumbs from flickering when rendered inside app layout toolbar breadcrumbs slot

[just-boris]

Description

Follow up for #2892.

When breadcrumbs are already rendered in the expected slot, there is no need for the runtime API interactions. This allows for a fast track without additional re-renders.

Related links, issue #, if available: n/a

How has this been tested?

1. Updated relevant unit tests
2. Tested the actual flickering locally on the dev page

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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[just-boris]

This is needed, because by default React.createContext produces a new context for each call. In our case, there could be multiple copies of this file, which will not allow context providers connect to its consumers.

We solve it by caching context instances by their name

[jperals]

But we are guaranteed to have only one copy of SharedReactContexts —do I understand correctly?

[just-boris]

Yes, because awsuiPluginsInternal object is deduplicated.

components/src/internal/plugins/api.ts

Lines 62 to 63 in 01aecc9

	const existingApi = findUpApi(win);
	win[storageKey] = installApi(existingApi ?? {});

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.21%. Comparing base (b22ec75) to head (cfc86a8).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #2895    +/-   ##
========================================
  Coverage   96.21%   96.21%            
========================================
  Files         761      763     +2     
  Lines       21511    21531    +20     
  Branches     7366     6972   -394     
========================================
+ Hits        20697    20717    +20     
- Misses        761      806    +45     
+ Partials       53        8    -45     

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[just-boris]

Technically, this is a breaking change. But this the new expected one, we should be fine.