[release/9.4] Force async execution of resource startup

[github-actions]

Backport of #10359 to release/9.4

/cc @davidfowl

Customer Impact

• Fixes an issue where resource startup could be blocked by a single blocking call, potentially delaying the startup of other resources.
• Improves reliability and startup performance, especially in scenarios where resources might perform blocking operations during startup.
• Issue was reproduced while dogfooding the community toolkit with 9.4 builds and this fix unblocks those scenarios.

Testing

• The issue was reproduced and verified fixed on the same 9.4 build during real-world usage (dogfooding).
• Manual validation demonstrates that resource startup no longer hangs due to blocking operations.

Risk

• Low to moderate: The change preemptively dispatches to the threadpool for each resource on startup, which is a targeted behavioral change.
• There is a minor risk that this could expose latent issues in resource startup ordering, but it is unlikely to negatively impact existing scenarios.

Regression?

• No. This change is a fix for a regression observed with 9.4 builds, where resources could hang on startup due to blocking calls.

[davidfowl]

I cherry-picked #10361 into this PR.