Cover: Adds Clear media button in block settings

[antonis]

Fixes WordPress/gutenberg#23789 (parent #2275)

Related PRs:

• Gutenberg [Mobile] Cover: Adds Clear media button in block settings WordPress/gutenberg#23794
• Create cover block with only colour from a default palette [Mobile] Create cover block with only colour (from a default palette) without an image WordPress/gutenberg#23833
• Create cover block with custom colour [Mobile] Create cover block with custom colour (without an image) WordPress/gutenberg#23870
• Media Button when only colour is selected [Mobile] Cover: Add Media Button when only colour is selected WordPress/gutenberg#23878

Description

Adds Clear media button in block settings

How has this been tested?

• Add a cover block
• Press the ADD IMAGE OR VIDEO button and select a media
• Tap on the block settings
• Verify that there is a clear media button that removes the set image

Screenshots

With set media	Without set media

Types of changes

Enhancement

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered if this change warrants user-facing release notes more info and have added them to [RELEASE-NOTES.txt](RELEASE-NOTES.txt) if necessary.

[peril-wordpress-mobile]

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[geriux]

Approved via WordPress/gutenberg#23794 (review)