fix(agw): Modified code to port spgw's state contexts to protobuf structure

[rsarwad]

Summary

fix(agw): Modified code to port spgw's state contexts to protobuf structure

Test Plan

Executed s1ap sanity test suite and unit test cases

[github-actions]

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[github-actions]

[cpplint] _{reported by reviewdog 🐶}
Using C-style cast. Use reinterpret_cast<void**>(...) instead [readability/casting] [4]