Fix irregular whitespace for MetadataRepresentationListComponent

[alexandrevryghem]

Description

Removed the trailing whitespace below the MetadataRepresentationListComponent when the page size is smaller than 10. Also reduced the spacing below the load more/hide last buttons to match the default spacing between item page fields.

Instructions for Reviewers

List of changes in this PR:

• Hide the mt-2 spacing from the load more/hide last buttons when the page size is smaller than 10
• Replaced the float-start & float-end styling on the load more/hide last buttons with flex box with justify-content: between. This will remove the additional spacing generated by the float logic underneath the buttons.
• Made the separator for this item page field configurable as well

Guidance for how to test and review this PR:

• Create a publication with 1 author
  • Verify that the spacing between the authors field & the next field is now the same as the other fields:
    →
• Create a publication with 10+ authors
  • Verify that the spacing between the authors field & the next field is now the same as the other fields:
    →

Checklist

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