Speed up the vaultik and database package tests (closes #235)

In the Dockerfile test phase, internal/vaultik spent 23.6s of 31.9s in
36 tests run one at a time. 24 of them were serial only because they
call log.Initialize; they now call it before t.Parallel(), so the
logger is replaced before any parallel test runs. The 12 still serial
change the umask, TMPDIR, os.Stderr or time.Local.

TestLargeDatasets took 8.4s of the 9.8s internal/database run by
committing each of its 1,500 inserts on its own; it now makes them in
one transaction. TestDedupOnlySnapshotRestores gives its second backup
its own snapshot name instead of sleeping 1.1s for a new snapshot ID.

Model: opus-5-5

internal/vaultik/missing_destination_test.go

@@ -78,10 +78,9 @@ func backUpThenUnplug(
 // TestFirstBackupCreatesDestinationDirectory checks that a first backup
 // to a destination directory that does not exist yet creates it, and
 // that the destination can be listed afterwards.
-//
-//nolint:paralleltest // installs the global logger via log.Initialize
 func TestFirstBackupCreatesDestinationDirectory(t *testing.T) {
 	log.Initialize(log.Config{})
+	t.Parallel()
 
 	ctx := context.Background()
 	storeDir := filepath.Join(t.TempDir(), "volume", "backup")
@@ -96,10 +95,9 @@ func TestFirstBackupCreatesDestinationDirectory(t *testing.T) {
 // TestListSnapshotsWarnsWhenDestinationMissing checks that snapshot list
 // warns and shows the local index alone, without reporting the local
 // snapshot as missing from the destination.
-//
-//nolint:paralleltest // installs the global logger via log.Initialize
 func TestListSnapshotsWarnsWhenDestinationMissing(t *testing.T) {
 	log.Initialize(log.Config{})
+	t.Parallel()
 
 	ctx := context.Background()
 	v, repos, out := backUpThenUnplug(ctx, t)
@@ -116,10 +114,9 @@ func TestListSnapshotsWarnsWhenDestinationMissing(t *testing.T) {
 // TestRemoveSnapshotWarnsWhenDestinationMissing checks that snapshot
 // remove warns that the metadata could not be removed from the
 // destination, instead of reporting that it was.
-//
-//nolint:paralleltest // installs the global logger via log.Initialize
 func TestRemoveSnapshotWarnsWhenDestinationMissing(t *testing.T) {
 	log.Initialize(log.Config{})
+	t.Parallel()
 
 	ctx := context.Background()
 	v, repos, out := backUpThenUnplug(ctx, t)
@@ -138,10 +135,9 @@ func TestRemoveSnapshotWarnsWhenDestinationMissing(t *testing.T) {
 // TestPruneKeepsLocalRecordsWhenDestinationMissing checks that prune
 // fails on a destination it cannot list and deletes no local snapshot
 // record.
-//
-//nolint:paralleltest // installs the global logger via log.Initialize
 func TestPruneKeepsLocalRecordsWhenDestinationMissing(t *testing.T) {
 	log.Initialize(log.Config{})
+	t.Parallel()
 
 	ctx := context.Background()
 	v, repos, _ := backUpThenUnplug(ctx, t)
@@ -158,10 +154,9 @@ func TestPruneKeepsLocalRecordsWhenDestinationMissing(t *testing.T) {
 // TestPurgeSaysListingFailedOnceWhenDestinationMissing checks that
 // snapshot purge fails on a destination it cannot list, with an error
 // that says "listing remote snapshots" once.
-//
-//nolint:paralleltest // installs the global logger via log.Initialize
 func TestPurgeSaysListingFailedOnceWhenDestinationMissing(t *testing.T) {
 	log.Initialize(log.Config{})
+	t.Parallel()
 
 	ctx := context.Background()
 	v, _, _ := backUpThenUnplug(ctx, t)