Added changes to generated api file under same package

[7h3-3mp7y-m4n]

What type of PR is this?

Added changes to Makefile to make protobuf generated api file under same package with .proto

/kind bug

What this PR does / why we need it:
This add nessacry change to Makefile to generate the file inside the same directory using protoc --proto_path=. --go_out=. --go_opt=paths=source_relative workloadapi/workload.proto
Which issue(s) this PR fixes:
Fixes #1024

Special notes for your reviewer:
checking to CI because of arm64

[kmesh-bot]

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[kmesh-bot]

Welcome @7h3-3mp7y-m4n! It looks like this is your first PR to kmesh-net/kmesh 🎉

[hzxuzhonghu]

I can run make gen-proto successfully in my AMD64 env.

But it is expected workload.pb.go to be in api/workloadapi/workload.pb.go instead of api/workloadapi/workloadapi/workload.pb.go

[hzxuzhonghu]

BTW, you can make other protobuf behave same