[http-client-java] codegen, ServiceVersion will be created multiple times when there are multiple clients

[haolingdong-msft]

Reproduce:
Use Communication.Messages to generate

Output:
There will be warning saying duplicate files found.

Root cause:

service version are created multiple times in below part of code:

https://github.com/microsoft/typespec/blob/main/packages/http-client-java/generator/http-client-generator-core/src/main/java/com/microsoft/typespec/http/client/generator/core/Javagen.java#L216-L226