Add license headers to all source files

[nascentcore-eng]

Context Right now, we use AGPL license, but source files have no license header.

Objective All source files should have license header

Proposed solution Skywalking-eyes could be used

First automatically add license header on all source files. And then add fossa check

[JaredTan95]

.licenserc.yaml defines : https://github.com/apache/skywalking-eyes/blob/main/.licenserc.yaml