Bug 3687 - StreamWriterGenerator emits UNKNOWN_SIZE

Bug 3687 - StreamWriterGenerator emits UNKNOWN_SIZE

StreamWriterGenerator always emitted sizing hint
for fully-completed data and sometimes even
counting all availble augmentations, which actually
lead-up to larger sizes of collections then needed.

Fix changes the SIZE HINT for "constant" max-sized
types (containers, augmentations, list entries)
to -1 so underlaying implementation could size
them based on actual data.

Change-Id: Ibd446f71c4b066f4dab4a7d73b1bc851d9e62c99
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>
Signed-off-by: Robert Varga <rovarga@cisco.com>