share: EDSStore.Get

[Wondertan]

Context

To read an entire EDS Get method is introduced.

Implementation Details

Internally it:

• Gets a serialized EDS io.Reader via EDSStore.GetCAR
• Deserializes the EDS and validates it via share.ReadEDS

// Get reads EDS out of Store by given DataRoot.
// 
// It reads only one quadrant(1/4) of the EDS and verifies the integrity of the stored data by recomputing it.
func (s *EDSStore) Get(context.Context, DataRoot) (*rsmt2d.ExtendedDataSquare, error)

Refs

Depends on #1109
Depends on #1107