[TASK] Add <typo3-backend-icon> component

The component is provided as replacement for the
current lit-helper `icon()` which cannot provide
support for icon usage inside shadow dom elements.

The component renders all icons as inline SVGs.
FontawesomeIconProvider is therefore adapted
to provide inline rendered SVGs for font-awesome
icons. Not that these inline font-awesome SVGs
will also be used in areas where 'inline' icons are
requested (like information toolbar) but the
fallback to 'default' was used before.

The component supports all properties of the
Icon API via HTML attributes.
Colors and custom sizes can be applied to the
component via CSS color/font-size property:

typo3-backend-icon[identifier=status-dialog-information] {
  color:#6daae0;
  /* An explicit font-size will be used as icon width & height */
  font-size: 1.2em;
}

Resolves: #93473
Releases: master
Change-Id: I3044c325f122eb0085ecb3f45fb9502bfb314d5d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67675


Tested-by: Richard Haeser <richard@richardhaeser.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Benni Mack <benni@typo3.org>