RequestBody/AsyncRequestBody from HTTP source

### Describe the feature

There are various `RequestBody`/`AsyncRequestBody` types that allow uploading files/buffers/Streams to S3. However, it would be great if the source can be HTTP (and HTTPS). Currently, one can fetch the file with their choice of HTTP client, and send to S3 clients. However, it requires dealing with low-level files/InputStream/OutputStream, and copying response headers, like content-type and content-length to the request headers for S3. This is also highly error prone in async context, i.e. dealing with non-blocking IO. The HTTP source should allow defining headers to pass in auth headers, etc.

### Use Case

It is frustrating to stream a file from another server to S3 in a performant way.

### Proposed Solution

_No response_

### Other Information

_No response_

### Acknowledgements

- [ ] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

### AWS Java SDK version used

2

Start by reviewing the existing RequestBody and AsyncRequestBody types and the S3 upload flow described in the issue. The work is complete when HTTP and HTTPS sources can stream uploads asynchronously, support caller-defined headers, and preserve relevant source metadata such as content type and length.

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