This is fairly minor because usually SVGs aren't focusable, but this
adds `aria-hidden='true'` to all SVGs by default unless either an
`aria-label` or `label` is provided. This gets reported to us in
automated tests from time to time.
So now:
1. SVG: `aria-hidden="true"` (new behavior, safe default when no label
is provided)
2. SVG with `label` param: `aria-hidden="true"` and `sr-only` label is
provided
3. SVG with `aria-label` param: `aria-hidden="false"` and `aria-label`
is provided
As of #23867 this is now a real package, so updating the imports to
use the real package name, rather than relying on the alias. The
name change in the package name is because `I18n` is not a valid
name as NPM packages must be all lowercase.
This commit also introduces an eslint rule to prevent importing from
the old I18n path.
For themes/plugins, the old 'i18n' name remains functional.
