Interactivity API: Fix context inheritance from namespaces different than the current one

[DAreRodz]

What?

Fixes a bug introduced in the recent refactoring of the Interactivity API internals (see #62734). Noticed while merging trunk in #62906.

Why?

The data-wp-context directive stopped propagating values from parent contexts using a different namespace. This broke directives trying to access values from such contexts.

Testing Instructions

These changes can be tested on top of the #62906 PR.

To reproduce the issue:

1. Checkout Gallery: Add lightbox support #62906 locally.
2. Merge trunk in the current branch.
3. Create a gallery on your test site with a couple of images.
4. Select "Expand on click" for each image.
5. Visit the page with the gallery.
6. When you expand an image, the buttons to navigate to the next and previous images don't appear.

To check the issue is fixed:

1. Checkout Gallery: Add lightbox support #62906 locally.
2. Merge this PR's branch in the current branch.
3. Follow steps 3 to 5 from the list above.
4. When you expand an image, the buttons to navigate to the next and previous images should appear.

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Co-authored-by: DAreRodz <darerodz@git.wordpress.org>
Co-authored-by: luisherranz <luisherranz@git.wordpress.org>

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[luisherranz]

LGTM! Thanks for the fix David.