Change tstest's exported functions (AssertNotParallel, Replace,
Parallel, RequireRoot, SkipOnKernelVersions, MinAllocsPerRun, FixLogs,
UnfixLogs, CheckIsZero, ResourceCheck) to take testenv.TB instead of
testing.TB or *testing.T, so importing tstest from non-test code no
longer links the testing package and its flag registration side
effects into the binary. Add testenv.Verbose to replace the one use of
testing.Verbose, and a deptest check to keep testing out of tstest's
dependency graph.
Callers are unaffected: *testing.T and testing.TB both satisfy
testenv.TB.
Updates tailscale/corp#45223
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Change-Id: Ib373ff66ceff638d071582baf8367245987e9155
3ccc7725a3