feat(storage): add a common blobstore to store all blobs (#3906)

Currently, zot uses one of the existing repos as the master copy for a blob to
achieve dedupe, which complicates dedupe tracking logic. Furthermore, we
have a global storage lock which is becoming a bottleneck. In order to
move to a per-repo lock, we first need to simplify this logic.

Now use a single hidden global repo (_blobstore/) as a blob store instead.

Signed-off-by: Ramkumar Chinchani <rchincha.dev@gmail.com>

pkg/cli/server/verify_retention_test.go

@@ -476,7 +476,7 @@ func TestRetentionCheckWithRetentionEnabledAndRedisDriver(t *testing.T) {
 
 		defer ctrlManager.StopServer()
 
-		os.Args = []string{"cli_test", "verify-feature", "retention", "-l", logFile, "-t", "2s", configFile}
+		os.Args = []string{"cli_test", "verify-feature", "retention", "-l", logFile, "-t", "10s", configFile}
 		err = cli.NewServerRootCmd().Execute()
 		So(err, ShouldBeNil)