Fix: Fix colorHex to handle alpha values

[laxa88]

Issue #, if available:

• Inconsistent support for alpha colors #362 (comment)

Description of changes:

By default, when using the js transformGroup, all tokens are converted into hex values (for example, #000000) before additional transforms are applied. For rgba tokens, this causes the color values to lose the transparency value, resulting in all tokens to default to #xxxxxxFF (full opacity).

This PR fixes the default transform to use hex8 to account for RGBA transforms.

I'm not entirely sure if there is a historical reason for using colorHex instead of colorHex8 for js transforms, but if this is not an oversight, I would appreciate if someone can share some details. Otherwise, I hope this PR helps. 🙇

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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[jorenbroekema]

Hi, I think this is mostly an oversight to be honest, I actually would prefer if we didn't have 2 transforms in the first place and just have 1 that handles both hex8 but also uses hex6 when the alpha channel is set 1.
So if possible, can we adjust the regular hex transform to handle hex8 when necessary and deprecate the hex8 specific transform, so we can remove it in the next breaking change but start telling users to use the regular hex one instead?

And can we add some tests to the PR?

[laxa88]

@jorenbroekema Thank you for the info and feedback.

• Reverted the change to colorHex8
• Updated the colorHex logic to handle hex6 and hex8, similar to colorCss
• Added and updated colorHex tests