Create googlesitekit-data variant for use in Site Kit's Gutenberg blocks

[techanvil]

Feature Description

We should create a variant of googlesitekit-data for use in Site Kit's Gutenberg blocks. This will be a subset of the googlesitekit-data store which uses the external @wordpress/data package (this is mapped to @wordpress-core/data in our block builds).

The primary driver of this update is to enable the use of useSelect() in Site Kit's blocks. We currently have a workaround in place for existing blocks, but it's not a long-term solution.

Notes:

• We currently patch @wordpress/data 4.27.3 to fix a bug which is present until version 9.0.0. Version 9.0.0 of @wordpress/data was published with Gutenberg version 15.5.0. Therefore, we need to wait until Site Kit's minimum version of WordPress is 6.4 or above before we can reliably use Site Kit's selectors in blocks via useSelect() in the same way that we do in the rest of Site Kit.
• However, we can still make use of useSelect() before this, but only when we can ensure that the bug doesn't have any impact on the functionality of the block. This means being aware that stores which are not selected in the first render will not be subscribed to, and so will not trigger a re-render when their data changes. See Update @wordpress/data to version 4.27.3 #6356 (comment) for more details.
• Either way, we still need to wait until Site Kit's minimum version of WordPress is 5.9 if we want to use selectors which call resolveSelect(), as this is __experimentalResolveSelect() until @wordpress/data version 4.27.0, which was published with Gutenberg 10.3.0.
• See also: discussion on the block issues document.

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