Issue #3355381 by catch, drewcking, stewest, lauriii, bnjmnm, lmoeni, fngatia, kevinquillen, Danny Englander, Ambient.Impact, gapple, manikandank03, lucasvm: Investigate better ways to add anti-flicker JS

Revert "Issue #3355381 by catch, drewcking, stewest, bnjmnm, lmoeni, fngatia, kevinquillen, Danny Englander, Ambient.Impact, gapple, manikandank03, lucasvm: Investigate better ways to add anti-flicker JS"

This reverts commit 56e2560a.

Issue #3355381 by catch, drewcking, stewest, bnjmnm, lmoeni, fngatia, kevinquillen, Danny Englander, Ambient.Impact, gapple, manikandank03, lucasvm: Investigate better ways to add anti-flicker JS

Issue #3101922 by bnjmnm, nod_, lauriii: Find replacement for Modernizr touchevent test and deprecate

Issue #3258931 by nod_, hooroomoo, xjm, catch, effulgentsia, Wim Leers: Deprecate backbone and tag it internal

Issue #2535118 by longwave, Wim Leers, borisson_, effulgentsia: Toolbar subtrees not working on admin pages due to lack of theme negotiation on Toolbar's custom JSONP route

Issue #2207629 by droplet, tarekdj, Devin Carlson, rpayanm: Update matchMedia library to latest release

Issue #1996238 by sun, nod_, damiankloip, Wim Leers, longwave, alexpott, Xano, mdrummond, Mark Carver, Jeff Burnz, highrockmedia, joelpittet, et al: Replace hook_library_info() by *.libraries.yml file.