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 #2910883 by vaplas, ShawnB, Wim Leers: Move all entity type REST tests to the providing modules

Issue #2765959 by davidwbarratt, Wim Leers, dawehner, borisson_, tstoeckler, tedbow, catch: Make 4xx REST responses cacheable by (Dynamic) Page Cache + comprehensive cacheability test coverage

Issue #2866252 by arshadcn, rakesh.gectcr: Refactor \Drupal\Tests\rest\Functional\EntityResource\Block\BlockResourceTestBase::getExpectedCacheTags

Issue #2815845 by dawehner, Wim Leers, alexpott, tedbow, Berdir, swentel, webflo: Importing (deploying) REST resource config entities should automatically do the necessary route rebuilding

Issue #2808233 by gnuget, dawehner, Wim Leers, tedbow, Chi, dysrama: REST 403 responses don't tell the user *why* access is not granted: requires deep Drupal understanding to figure out

Issue #2113345 by dawehner, tedbow, Wim Leers, kristiaanvandeneynde, Crell, Grayside, klausi: Define a mechanism for custom link relationships

Issue #2737719 by Wim Leers, dawehner: EntityResource: Provide comprehensive test coverage: for every entity type, every format, every method

Revert "Issue #2737719 by Wim Leers, dawehner: EntityResource: Provide comprehensive test coverage: for every entity type, every format, every method"

This reverts commit 59781ffc.

Issue #2737719 by Wim Leers, dawehner: EntityResource: Provide comprehensive test coverage: for every entity type, every format, every method