Add test for coerced type (read/write API for FPGA)

[amehra-ni]

What does this Pull Request accomplish?

The int32 and int64 implementations are similar as neither of them are coerced. Therefore, I have updated the int32 test to an int16 test to ensure we can test both behaviors.

Why should this Pull Request be merged?

• For the read API, I updated the read type to int16_t to match what is read from the real API.
• For the write API, I kept the type as pb::int32 since this is the value passed from the gRPC API to our server and then to native.

What testing has been done?

• All tests pass successfully.