allow serializing multidoc jq output back into yaml

[clux]

consider this command that provides multidoc of json as jq output:

$ cat test/deploy.yaml | yq '.[].metadata' -c
{"name":"controller","namespace":"default"}
{"name":"controller"}
{"name":"controller"}
{"labels":{"app":"controller"},"name":"controller","namespace":"default"}
{"labels":{"app":"controller"},"name":"controller","namespace":"default"}

what if we want this in yq output?

we'd currently have to do compact output and pass each line to yq.

we should be able to just pass -y to the above query, but that fails;

Error: trailing characters at line 5 column 1

we need to try to speculatively parse jq output in the same way we read the input yaml; by iterating over the Deserializer, and;

• if it has exactly one entry; deserialize into a serde_json::Value
• if it has many entries; deserialize into a Vec<serde_json::Value> (zero entries get an empty vec)

and after that convert it to yaml.