[release/7.0] Dispose CTS in HubConnection streaming

[github-actions]

Backport of #51117 to release/7.0

/cc @BrennanConroy

Dispose CTS in HubConnection streaming

Description

Fixes a memory leak in the SignalR client when using streaming.

Customer Impact

Noticed by customer when running a service with a client for multiple weeks and seeing large memory usage. Could also be seen by a more active client that makes a lot of streaming calls.

Regression?

• Yes
• No

Looks like it's been there since 3.X

Risk

• High
• Medium
• Low

Simple disposal of an object once it's done being used.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

[ghost]

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[ghost]

Hi @github-actions[bot]. This PR was just approved to be included in the upcoming servicing release. Somebody from the @dotnet/aspnet-build team will get it merged when the branches are open. Until then, please make sure all the CI checks pass and the PR is reviewed.

[wtgodbe]

@BrennanConroy @halter73 I can merge this once it gets code reviewed

[wtgodbe]

Components failure is unrelated & has been fixed, merging