Use MetadataUpdater.IsSupported to determine if application supports …

[pranavkm]

…hot reload

Fixes #33477

[ghost]

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[pranavkm]

The runtime is using MetadataUpdate as the term for hot reload. Updated this API to use this nomenclature. Outside of this, this PR is fairly simple - it uses the new API and adds a test hook for code that currently relies on testing. Once the SDK change - dotnet/sdk#18810 lands, we're able to trim out all[1] references to hot reload specific code.

[1] Right now the test type with the property set to default ends up not being trimmed. But it seems like a small cost and I'll follow up to see if we can clear that up. I wouldn't block on it though.

[pranavkm]

Could I have this reviewed? It's an easy one.