Release 5.3.0

Thanks to Peter for all these improvements and fixes!

Better use of screen space on mobile:
* urlbar: Hide #trust-label
* tabmenu: hide private browsing indicator and related widths
* findbar.css: remove features, save space
* boot.sys.mjs: set browser.ipProtection.enabled to false (hides Firefox
  VPN advertisement, can be enabled in about:mobile)
* aboutmobile: set browser.ipProtection.enabled

Refactoring:
* urlbar: remove private browsing indicator related code
* private-browsing-indicator.css: new common implementation vert and horizontal tab

Fixes:
* tabcounter: fix tabcounter position for FF 152+
* sidebar: fix width on FF 151
* preferences: hide policies hint again