[Style] Set fixed top menu bar height

[huchenlei]

Ref:

• [Feature Request]: [ Aesthetics ] Match the "small" Sidebar to the Topbar dimensions #1992
• Horizontal scroll workflow tabs on overflow #2188

Having top menu bar height vary with content is generally a bad design, as the extra height really screws up the overall styles. Considering we are also hosting extension-added widgets on the top menu bar. Using REM here to account different browser font size.

[JorgeR81]

I have a 1920 x 1080 display.
For me the Top bar it's 39 pixels height.

If the Top bar now has a fixed height, why not make it 40 pixels, instead ?

This way:

• The Top bar would have the same exact thickness as the small Sidebar.
• The Queue button would have a margin of 2 pixels above and below. 
  This is how it looks now: ( 1 pixel above, 2 below )

[jeery-star]

The design is not reasonable, can not adapt to the screen, really do not know what the designer has in mind, anti-human design

[webfiltered]

@jeery-star Please open an issue if you are having an issue.