Block Editor: Bug fixes targetted for WordPress 5.3 RC3.

The list of included fixes is:

- https://github.com/WordPress/gutenberg/pull/18108
- https://github.com/WordPress/gutenberg/pull/18051
- https://github.com/WordPress/gutenberg/pull/18106
- https://github.com/WordPress/gutenberg/pull/18102

Updated packages:
 - @wordpress/api-fetch@3.6.4
 - @wordpress/block-directory@1.0.4
 - @wordpress/block-library@2.9.4
 - @wordpress/core-data@2.7.4
 - @wordpress/data-controls@1.3.4
 - @wordpress/edit-post@3.8.4
 - @wordpress/editor@9.7.4
 - @wordpress/list-reusable-blocks@1.8.4
 - @wordpress/media-utils@1.2.4
 - @wordpress/server-side-render@1.3.4

Props desrosj.
See #48447.

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git-svn-id: https://core.svn.wordpress.org/trunk@46403 1a063a9b-81f0-0310-95a4-ce76da25c4cd