Ensure AWSLambdaRuntime only links FoundationEssentials

[fabianfett]

Ensure AWSLambdaRuntime only links FoundationEssentials

Motivation:

• We want to have great startup performance. Key to a quick startup is small binary size.
• When we use JSON today, we link complete Foundation
• FoundationEssentials was introduce to solve this issue

Modifications:

• Drop the dependency on NIOFoundationCompat, as it links the full Foundation and can only drop this dependency with the next major.
• Vendor necessary files from NIOFoundationCompat

Result:

• For a small HelloWorld that uses JSON, we are now at 9.2MB zipped.