Intent of TestDecodeHistories, TestDecodeOldHistories

All 2 exact tests in this concept. Every test is marked by where it enters the hierarchy.

go.temporal.io/ 2 tests
- server/ 2 tests
  - common/ 2 tests
    
    codec/ 2 tests
    
    TestJSONPBEncoderSuite/ 2 tests
    
    go.temporal.io/server/common/codec/TestJSONPBEncoderSuite/TestDecodeHistories Introduced here
    
    go.temporal.io/server/common/codec/TestJSONPBEncoderSuite/TestDecodeOldHistories Introduced here