Changed $radius default value to true

The docs indicate this as the default value, and the $global-radius and $button-radius values are indicated as being used by default throughout the core.
set radius to true in button-style mixin
Remove unnecessary top css property

The css property top: 1px; has no positive impact (for example if you want a background color for the whole tabs bar you will see this 1px breaking the visual consistency) on the tabs, so just remove.
deleted unnecessary .top-bar background-settings

fix for issue #4486
Topbar menu icon color when toggled
Fix for topbar color for .has-form a tags changes when hovered nearby
Fix: variable for $topbar-link-padding not used for horizontal padding on links
Added tab-bar class to offcanvas menu-icon.
Resolves conflict with topbar menu-icon
Added radius to a non-anchor current pagination item
Merge pull request #4454 from serquhart/button-radius-default-true

Button radius default true
Merge pull request #4484 from serglo/patch-4

Remove unnecessary top css property
Merge pull request #4487 from wolfgang-demeter/master

deleted unnecessary .top-bar background-settings
Merge pull request #4493 from Ilyes512/patch-1

Added radius to a non-anchor current pagination item
Merge pull request #4496 from NikhilKalige/topbar-icon-color

Fix topbar menu icon color when toggled
Merge pull request #4502 from NikhilKalige/top-bar-hasForm-hover

Fix for topbar color for .has-form a tags changes when hovered nearby
Merge pull request #4511 from jeroencoumans/master

Variable for $topbar-link-padding is not used for horizontal padding on links
Merge pull request #4522 from NikhilKalige/topbar-menu-icon-not-visible-fix

fix for topbar menu icon not visible