Let's support at least reading "b3" header from a single string, most commonly traceid-spanid-1
It would also be nice to support optionally writing this, especially in message providers or others with constrained environments.

Expected behavior

As discussed on openzipkin/b3-propagation#21 and first implemented here: https://github.com/openzipkin/brave/blob/master/brave/src/main/java/bra

JSON Lines is another JSON serialization format that can send a stream of JSON data.
Currently, Armeria only supports JSON Text sequences format using [JsonTextSequences](https://github.com/line/armeria/blob/67c25e242e8604331bdd8696a97d26604eb114af/core/src/main/java/com/linecorp/armeria/server/streaming/JsonTextSequences.java

Unused imports are included in the headers of generated files causing 2.12 builds with the default -Yfatal-warnings` setting to fail (unless the correct linting options are unset)

Expected behavior

Scrooge generates files with headers including only the imports the current file needs.

Actual behavior

Scrooge generates import statements for classes that are never used.

St