Switch to sending results complying with KCIDB I/O Schema v4

[spbnick]

KCIDB v9 is released, deployed, and now accepts I/O Schema v4.

Changes from the currently-used v2 are summarized in https://github.com/kernelci/kcidb/releases/tag/v6 and https://github.com/kernelci/kcidb-io/releases/tag/v3

Consider switching to sending data complying with KCIDB I/O Schema v4.

[spbnick]

@mgalka, promised to take care of this as well, IIRC.