[composer] Add createCommandWriter to command engine.

Command engine always uses V2.1 CommandWriterBase, change the creation of
command writer inside command engine so that we can use the right version of
command writer.

BUG: b/147365206
Test: build and boot.
Change-Id: I61fbbce19a44244725621e9a1cef750bd4c78b4d
3 files changed