feat: Add not-started status type for StatusIndicator

[Who-is-PS]

Description

This PR adds a new not-started status type to the StatusIndicator component to provide a distinct visual indicator for items that haven't begun processing yet.

Changes:

• Added 'not-started' to StatusIndicatorProps.Type union
• Created status-not-started.svg icon (simple circle)
• Updated StatusIndicator internal mapping to support new status
• Updated icon interfaces and provider

Related links, issue #, if available:
AWSUI-61005

How has this been tested?

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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