Dispose CTS when the Stream is claimed or timeout occurs

[clegoz]

Dispose CTS when the Stream is claimed or timeout occurs

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Summary of the changes (Less than 80 chars)

Description

Store the CancellationTokenSource to dispose when the DotNetStreamReference is claimed or timeout occurs.

Fixes #59263

[dotnet-policy-service]

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[lewing]

the existing code appears to prefer to check LeaveOpen and dispose the stream directly rather than just calling Dispose (which does the same check). I'm not familiar with the history but is there a guiding style principle here @javiercn

[lewing]

Thank you very much for the contribution. The changes look correct to me but I'll let others more familiar with the code do the final approval.