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/integration_test.go

@@ -928,17 +928,17 @@ func setupDedupBackupEnv(
 	}
 }
 
-// runDedupSnapshot creates a "dedup" snapshot, scans dataDir into it,
-// completes it, and exports its metadata, returning the snapshot ID and
-// scan result.
+// runDedupSnapshot creates a snapshot with the given name, scans dataDir
+// into it, completes it, and exports its metadata, returning the snapshot
+// ID and scan result.
 func runDedupSnapshot(
 	ctx context.Context, t *testing.T,
 	sm *snapshot.SnapshotManager, scanner *snapshot.Scanner,
-	hostname, dataDir, dbPath string,
+	hostname, name, dataDir, dbPath string,
 ) (string, *snapshot.ScanResult) {
 	t.Helper()
 
-	id, err := sm.CreateSnapshotWithName(ctx, hostname, "dedup", "v", "g")
+	id, err := sm.CreateSnapshotWithName(ctx, hostname, name, "v", "g")
 	require.NoError(t, err)
 
 	result, err := scanner.Scan(ctx, dataDir, id)
@@ -980,16 +980,15 @@ func TestDedupOnlySnapshotRestores(t *testing.T) {
 
 	// First snapshot — uploads all blobs.
 	_, r1 := runDedupSnapshot(ctx, t, sm, makeScanner(),
-		cfg.Hostname, dataDir, dbPath)
+		cfg.Hostname, "first", dataDir, dbPath)
 	require.Positive(t, r1.BlobsCreated,
 		"first snapshot should upload at least one blob")
 
-	// Second snapshot — same data, every chunk dedups. Sleep past the
-	// second-precision timestamp so the snapshot IDs differ.
-	time.Sleep(1100 * time.Millisecond)
-
+	// Second snapshot — same data, every chunk dedups. Its own name gives
+	// it a different snapshot ID without waiting for the one-second
+	// timestamp in the ID to tick over.
 	id2, r2 := runDedupSnapshot(ctx, t, sm, makeScanner(),
-		cfg.Hostname, dataDir, dbPath)
+		cfg.Hostname, "second", dataDir, dbPath)
 	require.Equal(t, 0, r2.BlobsCreated,
 		"second snapshot should upload zero new blobs (fully dedup'd)")