Evenly spread space between tabs (#12944)

Evenly spread space between tabs (#12944)

This commit fixes uneven spread of space between the tabs in profiles
or notifications (filters). The problem was that links and buttons
shown as blocks had their width determined according to the content
inside of them, so if one tab has more text content than another, it
is going to take over others space, which is uneven and results in
incorrectly aligned (?) tabs display.

By specifying the size of 100% for each tab, parent container will be
forced to divide available space by the number of elements and evenly
give each child fixed space, "text-align: center" then doing its best
job to keep tabs text centered in that space. This relatively fixes
the problem, but will introduce another one - when the block has more
content that its width allows to have, in this scenario the text should
be wrapped or will be displayed over the other elements, but I see this
more as translators' problem. Still, for this case "overflow: hidden"
is added and any unfitting text will be cut out.