Issue #3112452 by lalitware, guilhermevp, narendra.rajwar27, WagnerMelo, ravi.shankar, mradcliffe, adalbertov, himanshu_sindhwani, quondam, Vidushi Mehta, alexpott, longwave, anmolgoyal74: Fix indentation consistency in core's yaml files

Issue #2424805 by mdrummond, YesCT, vijaycs85, xjm, marcoscano, ifrik, joelpittet, Jelle_S, attiks, lauriii: Toolbar can no longer switch horizontal and vertical -- expects breakpoints ordered from smallest to largest; responsive images need largest to smallest

Issue #2260061 by Jelle_S, attiks, Wim Leers, mdrummond, mgifford, holist: Responsive image module does not support sizes/picture polyfill 2.2

Issue #2271529 by attiks, alexpott, Lowell, YesCT, Jelle_S | mdrummond: Move breakpoint settings to theme and module *.breakpoints.yml files at root level.