Fix snippet generation pipeline.

[andrueastman]

This PR fixes the timing out of the snippet generation pipeline caused by the error in the metadata capture in microsoft/OpenAPI.NET.OData#414

In summary, changes include

• Trace out errors in the openApi metadata(similar to Kiota) rather than throwing an InvalidOperationException to allow for generation where possible.
• Updated SimpleLazy to only acquire the lock when uninitialized to prevent unnecessary waits/locks on reads increasing generation time..
• Cache ISnippetsGenerator instances in the CodeSnippetsReflection.App to avoid multiple loads of the metadata increasing generation time.

Sample run can be found at here with generation time cut down to about 15mins from 40+ mins

[sonarcloud]

SonarCloud Quality Gate failed.   

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40.5% Coverage
0.0% Duplication

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