Add Solaris icons for light/dark mode

[julien-deramond]

Description

This PR changes the light/dark icons used in the theme selector to use Solaris icons:

• UI Light Mode
• UI Dark Mode

UI Auto Mode Solaris icon is not yet available and will be updated later on.

The rendering is the following:

Technical

Note: icon sizes have been specified by @Franco-Riccitelli

• Icons (sun, moon, auto, and tick) size: 20px x 20px (in the toggle button and in the dropdown menu items)
  • @Franco-Riccitelli This is treated as a specific rendering within the documentation and so not as an official variant of the dropdowns containing icons. It could maybe be a new variant within the DSM and Boosted
• Caret size: 10px x 5px
  • This size is the same as in our current dropdowns so I suggest creating a specific issue to tackle it within the whole framework (the current size is a bit too large)
• This PR changes the #check2 SVG used in the examples page as it wasn't the right one before (it was Bootstrap's)
• This PR includes the fix from Fix: make theme selector tick icon visible when active in examples layout twbs/bootstrap#39177 right now so that we can see the tick in example pages
• The rendering in light/dark mode is a bit broken on the examples page but this will be treated outside of this PR because probably linked to the basic rendering of other components in Boosted.

Live previews

• https://deploy-preview-2237--boosted.netlify.app/
• https://deploy-preview-2237--boosted.netlify.app/docs/5.3/examples/stickers/ (for example) for the other theme selector which is treated separately in our code

[netlify]

✅ Deploy Preview for boosted ready!

Name	Link
🔨 Latest commit	66b1784
🔍 Latest deploy log	https://app.netlify.com/sites/boosted/deploys/6502de39754da200085df875
😎 Deploy Preview	https://deploy-preview-2237--boosted.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[MewenLeHo]

Looks good to me and a11y is ok too.