Fix navbar wrapping on medium screens

[AndreaBarbasso]

References

• Fixes #3512

Description

Removed a white-space: nowrap rule, added some flex-shrink and flex-grow classes, and removed a flex-wrap class so that the navbar is not wrapping anymore on two lines.

Instructions for Reviewers

As said on #3512, on medium-sized screens the navbar could wrap on another row if there were more than 3 items in it. This PR introduces some template and style changes to avoid this behavior.

List of changes in this PR:

• Removed a white-space: nowrap; rule` that was wrapping the navbar onto another row;
• Added rules so that the navbar items could break on multiple rows and avoid overflowing of the right-hand side action buttons.

To reproduce the issue you can simply duplicate a navbar item and resize the screen. With this PR there is no wrapping or overflowing of items.

Checklist

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