[Admin][UI] Alert component

[chaimann]

Summary

Create a UI alert component following guidelines from Figma.
Split from #6228, as we'd need a proper way to show errors, and usage of UI toasts to communicate errors is discouraged as per guideline:

When not to use:
Avoid using toast for error messages. Always try to use a banner to prominently inform merchants about persistent errors.

Other stuff

• moved stimulus component controller from toast to controllers/alert_animation_controller as toast and alert share same animation behaviour;
• added an extra colour sazerac: "#fcf0dd", which is the same as the one used in designs for background of a warning alert (rgba(253, 192, 113, 0.25)), but without alpha channel (which would make the background half-transparent); name sazerac comes from the UI colors utility where this color is labeled "Sazerac" (which appears to be the name of a cognac-based cocktail)

Checklist

Check out our PR guidelines for more details.

The following are mandatory for all PRs:

• I agree that my PR will be published under the same license as Solidus.
• I have written a thorough PR description.
• I have kept my commits small and atomic.
• I have used clear, explanatory commit messages.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.87%. Comparing base (5c415e7) to head (74ca15d).
Report is 12 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6226   +/-   ##
=======================================
  Coverage   88.87%   88.87%           
=======================================
  Files         842      843    +1     
  Lines       18231    18240    +9     
=======================================
+ Hits        16202    16211    +9     
  Misses       2029     2029           

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