Switch to protobuf

[lujiajing1126]

WARNING: Huge amount of change has been made in this PR.

• Flatbuffers fully removed. (I guess there is still some references in go.sum)
• Protbuf introduced with adaptions made to fit with pb conventions.
• (Local) Tests Pass for pkg, banyand directories.
• License Check. (proto files are not supported by Skywalking-eyes, manually added. Skip *.pb.go and *.textproto)
• Use buf to lint and generate protos.

Problem found in this PR

Relative timestamp in ChunkID

The timestamp contained in chunkID is not the same as the timestamp field in the entity since we are using a relative time shift. This shift will cause inaccurate Scan results.

[hanahmily]

it looks good for now. We should improve the codes to pass the CI check. And I recommend leveraging buf to manage proto files.

[hanahmily]

Would we leverage https://github.com/bufbuild/buf to check proto files and generate stubs?

[lujiajing1126]

I've added buf.yaml and buf.gen.yaml to leverage buf.

I exclude two rules, i.e. RPC_REQUEST_STANDARD_NAME and RPC_RESPONSE_STANDARD_NAME since they require *Request and *Response for request and response types. Do we need to impose these two rules?

[lujiajing1126]

@hanahmily I need some help from you to setup CI workflow. It seems there is restriction of Actions usage in this repo.

Could you help setup the workflow?

[hanahmily]

@hanahmily I need some help from you to setup CI workflow. It seems there is restriction of Actions usage in this repo.

Could you help setup the workflow?

How about leave the workflow alone, let's merge it with some CI failures, I will submit another PR to fix them

[lujiajing1126]

@hanahmily I need some help from you to setup CI workflow. It seems there is restriction of Actions usage in this repo.
Could you help setup the workflow?

How about leave the workflow alone, let's merge it with some CI failures, I will submit another PR to fix them

Sure.