feat: Allow using an UploadedCode object for script processor's code parameter

[wimlewis-amazon]

Issue #: #3846

Description of changes:

Allows passing a UploadedCode as a code parameter to ScriptProcessor and ProcessingStep (instead of passing a path or URI which is internally converted to a ProcessingInput).

Testing done:

• existing unit tests pass
• new unit test added to cover this case
• my usage of this feature works-for-me

General

• I have read the CONTRIBUTING doc
• I certify that the changes I am introducing will be backward compatible, and I have discussed concerns about this, if any, with the Python SDK team
• I used the commit message format described in CONTRIBUTING
• I have passed the region in to all S3 and STS clients that I've initialized as part of this change.
• I have updated any necessary documentation, including READMEs and API docs (if appropriate)

Tests

• I have added tests that prove my fix is effective or that my feature works (if appropriate)
• I have added unit and/or integration tests as appropriate to ensure backward compatibility of the changes
• I have checked that my tests are not configured for a specific region or account (if appropriate)
• I have used unique_name_from_base to create resource names in integ tests (if appropriate)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[mufaddal-rohawala]

@wimlewis-amazon wanted to check in, as the PR is still in draft from past 2 weeks, is this ready?

[wimlewis-amazon]

Thanks for the checkin! I've decided I'm not sure this is the only/obvious way to expose this capability in the API, so I'm leaving this PR in draft state until I've discussed it with the Sagemaker Frameworks team.

[mufaddal-rohawala]

@wimlewis-amazon any update on this? lets have a internal discussion if needed on this.

[mufaddal-rohawala]

Resolving as the PR has been open for a while, please reopen as needed.