Fix slider error on Block creation

[Soare-Robert-Daniel]

Closes #1710

Summary

• Tweaked the hook that re-initializes the Glide instance when the num of images changes.
• Used a React Ref for getting the container for the Glide instance instead of making use of querySelector. This is working nicely in FSE and Widgets. But I still need the querySelector to check if the root is reachable by Glide -- e.g.: Inserter Block Review is not reachable.
• Solved another error related to the observer when deleting the block.

Screenshots

2023-08-21.17-40-43.mp4

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Test instructions

1. Create a new Slider Block.
2. Add some images.
3. The arrows that change the image position should work.

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Checklist before the final review

• Included E2E or unit tests for the changes in this PR.
• Visual elements are not affected by independent changes.
• It is at least compatible with the minimum WordPress version.
• It loads additional script in frontend only if it is required.
• Does not impact the Core Web Vitals.
• In case of deprecation, old blocks are safely migrated.
• It is usable in Widgets and FSE.
• Copy/Paste is working if the attributes are modified.
• PR is following the best practices

[pirate-bot]

Bundle Size Diff

Package	Old Size	New Size	Diff
Animations	270.78 KB	270.78 KB	0 B (0.00%)
Blocks	1.42 MB	1.42 MB	4 B (0.00%)
CSS	85.28 KB	85.28 KB	0 B (0.00%)
Dashboard	122.49 KB	122.49 KB	0 B (0.00%)
Export Import	83.17 KB	83.17 KB	0 B (0.00%)
Pro	303.27 KB	303.27 KB	0 B (0.00%)

[pirate-bot]

Plugin build for 2ff1ae6 is ready 🛎️!

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[pirate-bot]

E2E Summary

Typing

Test	Average Time (ms)	Standard Deviation (ms)	Median Time (ms)	Quantile for soft limit (%)	Quantile for hard limit (%)
Typing	88.99	12.71	86.84	0 (60ms)	21.05 (80ms)

Values above 60ms

"0 - 86.84, 1 - 77.92, 2 - 87.18, 3 - 73.29, 4 - 90.76, 5 - 79.99, 6 - 86.64, 7 - 90.57, 8 - 92.19, 9 - 101.75, 10 - 84.65, 11 - 134.33, 12 - 81.77, 13 - 96.72, 14 - 94.85, 15 - 82.27, 16 - 78.58, 17 - 81.83, 18 - 88.59"

[HardeepAsrani]

Looks good. During the testing, we can make sure to test it for backward compat & how it works in Widgets area and FSE.

[irinelenache]

@Soare-Robert-Daniel Tested and didn't find any problem 🚀

[pirate-bot]

🎉 This PR is included in version 2.4.0 🎉

The release is available on GitHub release

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