Interactivity API: Prevent calling proxifyContext with context proxies inside wp-context

[DAreRodz]

What?

Fixes a performance regression introduced in #62734, caused by proxifyContext being called over an already-proxified context repeatedly, thus increasing the number of proxies around the same context object every time a wp-context directive was rendered.
#62734

Why?

The ever-growing number of context proxies was causing the navigate() action to become exponentially slower.

The following pictures show the performance recording while clicking several times on the Next and Previous links in a Query block, before and after the changes containing the regression (#62734) are applied.

1. trunk at c384bb6 (before)
   

2. trunk at bd9ba41 (after)
   

How?

The fix prevents assigning to currentValue.current the result of calling proxifyContext( currentValue.current, ... ). This way, proxifyContext() never receives an already-proxified context as an argument when the wp-context directive is rendered multiple times.

Testing Instructions

1. Visit a page with a Query block. The block should have the "Force page reload" option disabled.
2. Repeatedly click on the Next and Previous links (over 20 times or more).
3. Without this PR, the clicks should become noticeably slower over time. With these PR changes, everything should be good.

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

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[gziolo]

That makes perfect sense as proxifyContext already return the proxified version of currentValue.current 👍🏻

I'll give it a round of testing just to be on the safe side.

@vcanales, it's something that we will have to include in the upcoming Gutenberg plugin release.

[gziolo]

In my testing, the issue is still not fully resolved. After 30 seconds of testing Query block and clicking prev/next, the page becomes unusable:

[gziolo]

Ok, something must have gone wrong with the way I tested. I can now confirm that the issue is fully resolved and the performance graph is comparable to WordPress 6.6: