TODO: aws slim down/refactor

[H-Plus-Time]

Prior art for this is object_store_s3_wasm for an aws-sdk + siblings based approach.

The original in arrow-rs/object_store is more or less a from-scratch implementation (with the exception of reqwest), and is likely a very bad idea to try to replicate here.

[H-Plus-Time]

The version inlined from object_store_s3_wasm includes a number of fairly beefy dependencies (after wasm-opt, the size delta for the aws feature is ~2.5MB on an initial size of 640kB). Hopefully most of those are largely unimportant (that is, we only use one or two structs, that could be inlined).