HUBS-1561 GO SDK version update for DCT 6.0

[kishlay-delphix]

This PR aims at updating the go-sdk to make it compatible with the latest version of DCT (6.0.0)

Problem:

While updating the go sdk we encountered a number of issues:-

1. Duplicate entries were created for enums.
2. Codegen.sh used to override existing files, what this meant was even after a new generation we would have files which were already present and are not needed in the current version.

Solution:

The above issues where solved in the following ways:-

1. Adding -p enumClassPrefix=true argument when using the jar to generate classes.
2. Cleanup of all existing go files and then generating all files.

Testing

Tested get environments and VDBs.

[sunnyx4]

1. can you put the JIRA issue in the subject?
2. can you summarize the issues we had seen in the existing code-gen and the steps taken to resolve them here in the PR?

[kishlay-delphix]

@sunnyx4 Done