Migrate Key-Value parser from stanza

[crobertson-conga]

Stanza recently included a key-value parser for logs:

https://github.com/observIQ/stanza/blob/main/docs/operators/key_value_parser.md

Several applications, like loki, leverage this instead of something like json for structured logs.

[djaglowski]

Hi @crobertson-conga. PR #307 would accomplish this. It's been stalled for a while but hopefully we'll see this completed soon. In the mean time, we did not have a tracking issue for that PR, so this issue can serve that purpose.

[jsirianni]

@djaglowski I will follow up on the PR feedback 👍