Refactor and move config resolution codegen logic from generic layer to AWS layer

[ubaskota]

Issue #, if available:

Description of changes:
Moved AWS-specific config resolution codegen (descriptors, validators, custom resolvers, default values) out of the generic ConfigProperty and ConfigGenerator into the AWS codegen layer. Introduced AwsConfigResolutionIntegration as a CodeInterceptor that transforms the generated Config class to inject descriptor support, resolver initialization, and source tracking. Each integration now owns its own property metadata (e.g., SDK_UA_APP_ID_METADATA lives in AwsUserAgentIntegration). The generic codegen layer (codegen/core/) has zero diff from develop.

Testing

• Verified that the config file is generated with descriptor, resolver and validators.
• Verified that the config file for the generic sdk is unchanged.
• Ran tests using the the generated config file and verified that all tests pass.

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