v23: syncbase: Explicitly pass in batch handle.

Batch handle is now passed in as an RPC argument instead of being
embedded in Vanadium object name. It is only passed into batch-aware
RPCs, making them easier to distinguish. Wired through client library.
Split DatabaseHandle methods out of client library database object
into databaseBatch as common ancestor of database and batch. This
increases type safety (especially in light of explicit BatchHandle
passing) and mirrors client libraries in other languages.
Made Collection.{Create,Destroy} callable inside batch.
Clarified glob vs ListCollections/Scan batch behaviour.

MultiPart: 1/2
Change-Id: I0b2fbcdfeebd6eb918030dad194eb22384703173
12 files changed