[FAB-7131] CouchDB: per channel-chaincode DB

For every chaincode, use a separate database instead of using
the same channel database. This CR makes the following changes:
(i) creates a database per channel_chaincode and two DBs per
channel_chaincode_collection (one for hashed data and another for
actual private data).
(ii) modifies GetState, RangeQuery, and ExecuteQuery implementation
to use appropriate chaincode DB as per the given namespace.
(iii) modifies commit process (ApplyUpdates) to apply changes to
respective chaincode DBs.

In the subsequent CR, for loadCommittedVersions and ApplyUpdates,
goroutines would be used to process each chaincode batches
parallely.

Change-Id: I05b5f70e6c253cec683382c9e5b2b39b6a6bcce8
Signed-off-by: senthil <cendhu@gmail.com>

core/ledger/kvledger/txmgmt/privacyenabledstate/common_storage_db.go

@@ -18,7 +18,7 @@ import (
 )
 
 const (
-	nsJoiner       = "/"
+	nsJoiner       = "$"
 	pvtDataPrefix  = "p"
 	hashDataPrefix = "h"
 )