[UnifiedDataTable] Redesign Document column

[kertal]

This issue aims to redesign the current way the Document column is rendered in Discover.

Current State:

Figma Redesign:

POC PR version:

Tasks:

• [x] Get rid of the background of the field names
• [x] Adjust paddings & margins so it fits the Figma (if possible)
• [x] Set the field names to semi-bold
• [ ] Add a field token to the field names
  • This is currently blocked due to the performance impact so we would need research an alternative to inline rendering of tokens
• [ ] Allow users to opt out of viewing the tokens via grid settings

Out of scope:

• Change the font face

Thinks to keep in mind

• Discover's data table becomes the UnifiedDataTable, so we have more than one consumer soon that will be impacted by this change
• For the tokens it could be a separate PR, for sure, if it makes sense

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)