reuse contrib resource providers + add existing ones

[SylvainJuge]

Add "resource providers" that allow to capture resource attributes (that we usually refer as cloud metadata).

AWS: https://github.com/open-telemetry/opentelemetry-java-contrib/blob/main/aws-resources/

bonus: application servers resource provider
https://github.com/open-telemetry/opentelemetry-java-contrib/tree/main/resource-providers

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Update the GCP one has been moved to a separate task/PR to allow merging this as it's getting quite large #27

[SylvainJuge]

This is currently blocked by two things:

• there isn't a single source for the resource providers, I opened Add resource providers for common cloud providers open-telemetry/opentelemetry-java-contrib#1074 as an attempt to solve this.
• (optional for now): adding the resource providers slows down the SDK init, asynchronous resource providers execution #19 should help improve this.