Remove `-custom-job` suffix from display names

Thanks for stopping by to let us know something could be better!

**PLEASE READ**: If you have a support contract with Google, please create an issue in the [support console](https://cloud.google.com/support/) instead of filing on GitHub. This will ensure a timely response.

**Is your feature request related to a problem? Please describe.**
When creating a `CustomPythonPackageTrainingJob`, I specify the display name:

`job = aiplatform.CustomPythonPackageTrainingJob(display_name='my-job', ...)`

but after calling `job.run(...)` (without specifying a `model_display_name` which is apparently no longer supported in `1.36.4`?), while the `Training Pipelines` tab shows the desired display name, the `Custom Jobs` tab shows that each job has `-custom-job` appended to the display name (i.e. `my-job-custom-job`). This display name is then used in other parts of the codebase, e.g. experiment tracking and Tensorboard.

**Describe the solution you'd like**
I would like to specify the display name of the custom job myself. Or simply use the same display name without appending `-custom-job` to it.
**Describe alternatives you've considered**
n/a
**Additional context**
Screenshot of undesired custom job display name: