testing/fstest: return structured errors in TestFS
TestFS now returns a structured error built with errors.Join to allow to
inspect errors using errors.Is and errors.As.
All errors are now wrapped using fmt.Errorf and %w.
Fixes #63675.
Change-Id: I8fc3363f8ae70085af4afdb84c16be9ca70d7731
Reviewed-on: https://go-review.googlesource.com/c/go/+/537015 Reviewed-by: Bryan Mills <bcmills@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>