Allow using active host context in hostfxr_get_runtime_delegate

[jander-msft]

These changes allow for passing nullptr for the handle parameter of the hostfxr_get_runtime_delegate function. This allows in-process callers who do not have the real host context handle to invoke this function and get a runtime delegate for the primary runtime instance. Calling hostfxr_get_runtime_delegate without the handle will only work if there is an active host context, otherwise it will return StatusCode::HostInvalidState.

For testing, I decided to add a new test specifically for ensuring that calling hostfxr_get_runtime_delegate without the handle will work instead of updating the existing tests. Most of the other tests would not have worked with this enablement because it requires an active context handle to be set, which only largely occurs if calling hostfxr_get_runtime_delegate with an existing handle or calling fx_muxer_t::run_app; rather than forcing these to unnecessarily invoke hostfxr_get_runtime_delegate twice (one with a handle, the next without), I created a separate test to do just that.

Fixes #84143

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Issue Details

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These changes allow for passing nullptr for the handle parameter of the hostfxr_get_runtime_delegate function. This allows in-process callers who do not have the real host context handle to invoke this function and get a runtime delegate for the primary runtime instance. Calling hostfxr_get_runtime_delegate without the handle will only work if there is an active host context, otherwise it will return StatusCode::HostInvalidState.

For testing, I decided to add a new test specifically for ensuring that calling hostfxr_get_runtime_delegate without the handle will work instead of updating the existing tests. Most of the other tests would not have worked with this enablement because it requires an active context handle to be set, which only largely occurs if calling hostfxr_get_runtime_delegate with an existing handle or calling fx_muxer_t::run_app; rather than forcing these to unnecessarily invoke hostfxr_get_runtime_delegate twice (one with a handle, the next without), I created a separate test to do just that.

Fixes #84143

Author:	jander-msft
Assignees:	-
Labels:	area-Host
Milestone:	-

[vitek-karas]

Looks good - I'll leave the final call to @elinor-fung .

[elinor-fung]

Looks good - just some minor comments. Thank you for doing this!

[jander-msft]

I'm going to hazard a guess that the single failure is not really due to my change. I don't see a way of rerunning that one build leg in GH or AzDO (maybe I just don't have permissions). Is there some way to do it without starting an entirely new build?

[vitek-karas]

Yes - they're unrelated. If you go to Checks and then on the left open Build Analysis, it shows that all the failures are known issues.

Thanks a lot for this PR!

[elinor-fung]

Thanks, @jander-msft!