Verify that "CBOR sequences" (RFC 8742) "just works" (or if not, make work)

[cowtowncoder]

So, as per RFC 8742:

https://www.rfc-editor.org/rfc/rfc8742.html

concatenation of root-level CBOR values should just work, quite similar to JSON and Smile.
Jackson API handles this case fine but need to verify that underlying streaming code does it as well.
For bonus points might want to verify that encoding also works.

If changes are needed, those should be targeted at 2.13; if everything works should just document to already work with 2.12.

[cowtowncoder]

Works as expected with Jackson 2.12 -- likely has worked much earlier, but marked "as-fixed" for 2.12.0 as it is now verified and tested with unit tests.