fix(sagemaker): singleton window bug

[aws-ajangg]

Problem

• When user connects to space, it creates a duplicate window for the same space

Solution

• Assign unique identifier to workspace. This will open same external window when connecting to same workspace.

---

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[amazon-inspector-ohio[bot]]

:hourglass_flowing_sand: I'm reviewing this pull request for security vulnerabilities and code quality issues. I'll provide an update when I'm done

[github-actions[bot]]

• This pull request modifies code in src/* but no tests were added/updated.
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[amazon-inspector-ohio[bot]]

:white_check_mark: I finished the code review, and didn't find any security or code quality issues.