SERVER-35169 Bump wire protocol version for 4.2.
SERVER-35752 Ensure tests that rely on FCV pass after updating FCV constants.
SERVER-35163 Unblacklist tests that expect FCV version to differ between "last-stable" and "latest."
SERVER-34984 Update major_version_upgrade.js to call setFCV to the latest FCV.
SERVER-35656 Ensure a 4.0 mongos crashes upon attempting to connect to an FCV 4.2 cluster.
SERVER-35404 Re-enable the sharding_last_stable_mongos_and_mixed_shards suite.