Respect default_bucket_prefix by default for Estimator code_location

**Describe the feature you'd like**
Currently the `code_location` attribute of the Estimator class defaults to using the `output_bucket` parameter [docs link](https://sagemaker.readthedocs.io/en/stable/api/training/estimators.html#sagemaker.estimator.EstimatorBase):

> If not specified, the default code location is ‘s3://output_bucket/job-name/’.

The [Session object also has a parameter](https://sagemaker.readthedocs.io/en/stable/api/utility/session.html#sagemaker.session.Session) `default_bucket_prefix` that can be configured.

Ideally, if
1. The `output_bucket` part of `output_path` is the `default_bucket`
2. `_is_output_path_set_from_default_bucket_and_prefix` is False

Then the default location should respect both the `default_bucket` as well as the `default_bucket_prefix`.

e.g. `s3://default_bucket/default_bucket_prefix/job-name/`

This change would be implemented in [_stage_user_code_in_s3](https://github.com/aws/sagemaker-python-sdk/blob/23109671f6262269ab54cdd9aeb5ebe4ea640d25/src/sagemaker/estimator.py#L1042).

Otherwise, the default behavior creates artifacts at the root of the bucket. This means that default behavior for environments where IAM bucket write access is limited by prefix (i.e. SageMaker Unified Studio) will fail.

**How would this feature be used? Please describe.**
If this behavior is implemented, model code assets would be uploaded by default to a prefix where write access is allowed.

**Describe alternatives you've considered**
Currently `code_location` needs to be manually configured to work in SageMaker Unified Studio. This is poorly documented as part of features like [ModelStep](https://sagemaker.readthedocs.io/en/stable/workflows/pipelines/sagemaker.workflow.pipelines.html#sagemaker.workflow.model_step.ModelStep) where it needs to be configured in `repack_model_step_settings` as the model.register output populates `output_path` by default in a pipeline.

If this change cannot be implemented in code, explicit documentation should be provided about configuring parameters to output code in the SageMaker Unified Studio project prefix.

Beginne in src/sagemaker/estimator.py bei _stage_user_code_in_s3 und prüfe anschließend die verlinkte Dokumentation zu Estimator und Session sowie die Referenzen auf ModelStep/repack_model_step_settings. Als erledigt gilt die Aufgabe, wenn der Standardspeicherort für den Code unter den angegebenen Bedingungen für den Ausgabepfad default_bucket_prefix verwendet und die Konfiguration dokumentiert ist, falls die Codeänderung nicht möglich ist.

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