[release/8.0] Dispose CTS in HubConnection streaming

[github-actions]

Backport of #51117 to release/8.0

/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]

Hi @github-actions[bot]. Please make sure you've updated the PR description to use the Shiproom Template. Also, make sure this PR is not marked as a draft and is ready-to-merge.

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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.

[ghost]

Looks like this PR hasn't been active for some time and the codebase could have been changed in the meantime.
To make sure no conflicting changes have occurred, please rerun validation before merging. You can do this by leaving an /azp run comment here (requires commit rights), or by simply closing and reopening.

[BrennanConroy]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[BrennanConroy]

@dotnet/aspnet-build can this be merged?