cmd/vet: bring in pass to catch invalid uses of testing.T in goroutines

Add "go/analysis/passes/testinggoroutine" from x/tools and vendor its source in.
This pass will catch misuses of:
* testing.T.Fail*
* testing.T.Fatal*
* testing.T.Skip*
inside goroutines explicitly started by the go keyword.

The pass was implemented in CL 212920.

While here, found 2 misuses in:
* database/sql/sql_test.go
* runtime/syscall_windows_test.go
and fixed them in CL 235527.

Fixes #5746

Change-Id: I1740ad3f1d677bb5d78dc5d8d66bac6ec287a2b1
Reviewed-on: https://go-review.googlesource.com/c/go/+/235677


Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>