blobpacked: start of untested blob streaming code

Will be used for recovery.

Change-Id: I8a6d219086a306e53b1b621b7bc7cf59b984c765
C+A: add Matthieu Rakotojaona (Individual CLA)

Change-Id: Ic24976e558c6e3d2ca0f7ebc987d09f1639af57c