[EnterprisePill] Fix profile menu spacing

The spacing between the title and the icon in the new profile menu is
set to the default of 8px. This updates the menu to set the spacing to
6px. As such, a new parameter is also added to the HoverButton to pass a
custom spacing down to the `IconWidget`. The default remains equal to
`DISTANCE_RELATED_LABEL_HORIZONTAL` (8px).

Screenshot: https://screenshot.googleplex.com/AkeQANkmibjzPUb

Bug: 391655525
Change-Id: Ia612751a2b7c65e5cde111892a3b41e46c257471
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6196521
Commit-Queue: Salma Elmahallawy <esalma@google.com>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Dana Fried <dfried@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1411716}