Loading component updates

[alex-maul]

This PR is for updating the Loading component to accept variants for our loading spinner. By default variant "primary" will display if an svg isn't provided. Variant "secondary" will display if passed to "iconVariant" and an svg isn't provided. If an "svg" is provided, the svg will take priority over variants and render the svg.

Lakefront PR Checklist

• [ ] Created new components following the contributing guide.
• [ ] Exported any new components in the src/index.ts.
• [ ] Updated the main README table.
• [ ] Ensure version numbers were bumped properly.
• [x] Imported SVGs with relative path, if applicable.
• [ ] Removed any irrelevant commit messages from merge commit.
• [ ] Deleted branch after merge.