Issue #2822382 by voleger, pfrenssen, erozqba, RytoEX, borisson_, sidharthap, Jo Fitzgerald, shashikant_chauhan: Make every  property protected on classes extending BrowserTestBase and KernelTestBase

(cherry picked from commit 69501f30)

Issue #2976334 by tedbow, Wim Leers, johndevman, tim.plunkett, phenaproxima, larowlan, samuel.mortenson, Berdir, EclipseGc, johnzzon: Allow Custom blocks to be set as non-reusable adding access restriction based on where it was used

(cherry picked from commit 98430f12)