[WIP] Address feedback on ObjectDisposedException handling in CosmosClient

[Copilot]

Thanks for the feedback on #5597. I've created this new PR, which merges into #5597, to address your comment. I will work on the changes and keep this PR's description up to date as I make progress.

Original PR: #5597
Triggering review: #5597 (comment)

@copilot please double check the order of setting isDisposed to True and setting the mutable fields to null in Dispose

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[FabianMeiswinkel]

@copilot there were no changes yet - are you still working on this PR?

[FabianMeiswinkel]

Fixed already

[github-actions]

Please follow the required format: "[Internal] Category: (Adds|Fixes|Refactors|Removes) Description"

Internal should be used for PRs that have no customer impact. This flag is used to help generate the changelog to know which PRs should be included. Examples:
Diagnostics: Adds GetElapsedClientLatency to CosmosDiagnostics
PartitionKey: Fixes null reference when using default(PartitionKey)
[v4] Client Encryption: Refactors code to external project
[Internal] Query: Adds code generator for CosmosNumbers for easy additions in the future.