Breaking Changes:

Added content type parameter to golioth_lightdb_observe_async().
Previously this defaulted to JSON. Existing projects can add
GOLIOTH_CONTENT_TYPE_JSON as the third param of this API call to
replicate behavior prior to this change.

Highlights:

Added the ability to cancel RPC and Settings observations
Updated Stream example and documentation to show usage of Golioth's
Pipelines feature.
Exposed additional APIs for downloading OTA components.
- This can be used to implement more complex update scenarios in the user
  application (i.e. outside of the SDK).
- Note that users who choose to implement their own update logic will need to
  manage applying the update and reporting state back to Golioth, tasks which
  are handled by the built-in, but more limited, firmware update module in
  the SDK.

Fixed swapped sync/async messages in Stream example
Stream example now works correctly with on-board temperature sensors
Target version is now set when reporting OTA status to UPDATING
Fixed memory leak when maxing out observations
LightDB State gets of JSON objects would strip leading and trailing
curly brackets
Fixed potential buffer overflow during string copy
Removed unused Kconfig symbols

Kconfig: reorganized how Kconfig options are presented in the
menuconfig interface.
Use CBOR in Stream example instead of JSON
Contribution and Style guides have been updated