fix(fxa-settings): align password CTA

[millmason]

Because:

• Since all other UnitRow components in the Security section have
  refresh buttons, the Password row CTA button seems out of alignment.

This commit:

• Adds a descriptive prop so that the user can align the CTA within a
  UnitRow with buttons that have a refresh button.

Closes #11972

Checklist

Put an x in the boxes that apply

• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).

Screenshots (Optional)

Before:

After:

RTL (before changes):

Other information (Optional)

Styles deliberately do not have the rtl prefix, as the position of the buttons does not change when the text direction of the page changes, as shown in the above screenshot. Has been tested in Arabic and Hebrew.

Looking at the new button alignment, I think it might be worth leaving the designs as they originally were -- to my eye the buttons have a slight optical illusion of being misaligned (even when they do line up) due to the buttons above the Security section all lining up flatly with the right-hand side of their container. I would really appreciate eyes + opinions on it!

[LZoog]

@millsoper 1st PR woot! 🎉

I know I just mentioned in Slack we need to push our branches to mozilla/fxa directly, and I think we'll have to close this and re-open it for Storybook to deploy. We could also see if screenshots will be sufficient on determining if we want this or not, though. 🤷‍♀️ The code changes LGTM.

[millmason]

Closing PR since I pushed it directly to mozilla/fxa per @LZoog 's comment above. New PR is at #12514