examples: zephyr: Add CBOR examples to lightdb_stream example app

[cdwilson]

Update the lightdb_stream example app to include sync & async examples showing how to send CBOR-encoded sensor data to LightDB Stream.

If you don't want the last commit (dc055c6464d0c34445f1a53275033b6e1dea2ca6) just LMK and I can drop it (was just trying to consolidate duplicate code)

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Visit the preview URL for this PR (updated for commit a18bb55):

https://golioth-firmware-sdk-doxygen-dev--pr469-cdwilson-zephy-nmtmtw62.web.app

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Code Coverage

Type	Coverage
lines	55.6% (1036 of 1862 lines)
functions	57.7% (94 of 163 functions)

[sam-golioth]

@cdwilson Can we add tests for the new functionality? Should be as simple as extending the number of temperature readings we're checking (in examples/zephyr/lightdb_stream/pytest/test_sample.y) to ensure that we're covering the new functions.