Add a rich preview to import

Rich preview

This merge request add a rich preview of the content that will be imported in an existing table.

On this screenshot, you can see a bifferenc with the initial design. I've kept the original file preview to make the field mapping more easy to do if the automatic mapping fails. I'd love to hear your thoughts about this.

Technically, this is an partial extract of the SelectRowContent to create a new component: the <SimpleGrid> which is used for both, initial file preview and importedData preview. In a next iteration we could be able to merge the SelectRowContent table and the SimpleGrid to keep only one component.

Merge Request Checklist

• changelog.md has been updated if required
• New/updated Premium features are separated correctly in the premium folder
• The latest Chrome and Firefox have been used to test any new frontend features
• Documentation has been updated
• Quality Standards are met
• Performance: tables are still fast with 100k+ rows, 100+ field tables
• The redoc API pages have been updated for any REST API changes
• Our custom API docs are updated for changes to endpoints accessed via api tokens
• The UI/UX has been updated following UI Style Guide

Closes #1120 (closed) Closes #1201 (closed)