Adjust RangeControl to add the stepper control and allow type selection

[chipsnyder]

Fixes: #1992
gutenberg WordPress/gutenberg#21465

Description

This PR refactors the RangeControl component to allow the optional parameter type to allow selection between the Stepper control or a slider control on Mobile.

Since the range control is being used in multiple places right now as a slider control, I made the slider the default option.

This PR also updates the gallery component to pass in type=stepper to test the other use flow. The gallery component was also the only place where I could find references to the stepper control.

How has this been tested?

Stepper:

1. Open a gallery block with multiple images
2. Expect to see the stepper control under the columns option

Slider:

1. Open a control using the RangeControl. Examples:

   • Button: Border Radius
   • Cover Block: Minimum height in pixels, Background opacity
   • Latest-Posts: Number of items, Excerpt length

2. Expect to see the slider control

PR submission checklist:

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

[peril-wordpress-mobile]

You can trigger optional full suite of UI tests for these changes by visiting CircleCI here.

[pinarol]

I am changing the milestone of this PR as 1.27 because the 1.26 release branch will be cut quite soon. Let me know if you instead wanted to include this to 1.26.

[geriux]

LGTM! Approved via WordPress/gutenberg#21465 (review)