Fix RangeControl mark placement and cursor styles

[stokesman]

RangeControl has the little-used feature of marks. Using the prop marks they can be placed automatically or specified ("custom" in the screenshots). The placement of specified marks will be incorrect if the step property is decimal or the min property is negative.

An example with step property as decimal:

Before	After

An example with min={ -10 } and max={ 10 }:

Before	After

In such cases not only are the custom marks out of place, (when value is undefined) the calculation for which marks are represented as "filled" is incorrect.

Additional changes not related to the aforementioned mark issues are minor styling changes to fix: #25345. Though it turns out those styling changes helped reveal a further issue with the marks. They obscure interaction with the input:

Not something that would occur often but glad to have caught it. Commit 8d8b31a1d9f0565dc674fd6ced219e7f94374aaf pushed to resolve that.

How has this been tested?

In Storybook using this story:
https://gist.github.com/stokesman/155ec2791493a3e9fe134ac6ee988235
In WordPress 5.5.1 with a custom block using a RangeControl with custom marks

Types of changes

Bug fix

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.

[stokesman]

While looking for existing issues I found these that appear outdated and able to be closed #12429 and #12432.

[stokesman]

@ItsJonQ, it'd be great if you can have a look (at your leisure, I don't think there's any urgency).

Currently, in Gutenberg, there are no instances of the use cases fixed by this PR. So for testing Storybook is easiest (but also lacks coverage of such use cases). This gist contains the story I used in testing. If it's deemed worthwhile I'm willing to add stories to this PR, but I'd like to know if there are some guidelines to follow for those additions.

[ItsJonQ]

@stokesman 🚀 from me! Thank you so much for the update! You're totally right. The previous implementation didn't correctly handle negative min values. The pointer-events fix is also very welcomed.

The gist you shared was very helpful! Do you think you'd be able to add that to the existing story? :)

I think it would be helpful for future testing and development.

Thanks! ✨