[IMPROVE] UI design for Tables and tabs component on Directory (#11026)

...ges/rocketchat-theme/client/imports/components/header.css

...tchat-theme/client/imports/components/modal/directory.css

...ages/rocketchat-theme/client/imports/components/table.css

packages/rocketchat-theme/client/imports/components/tabs.css

packages/rocketchat-theme/client/main.css

packages/rocketchat-ui-master/public/icons.svg

packages/rocketchat-ui/client/components/table.html

packages/rocketchat-ui/client/components/table.js

packages/rocketchat-ui/client/components/tabs.html

packages/rocketchat-ui/client/components/tabs.js

packages/rocketchat-ui/client/views/app/directory.html

packages/rocketchat-ui/client/views/app/directory.js

packages/rocketchat-ui/package.js

server/methods/browseChannels.js