Configure AWS SDK Automatically

[mustafaakin]

Looking at bottomless project readme and source code, it looks like it always expects AWS Access Key and Secret Key from ENV variables.

sqld/bottomless/src/replicator.rs

Line 140 in 146df90

secret_access_key,

However, in AWS computing, the SDKs should be able to auto-configure it from the multiple credential providers, so it works seamlessly in EC2, Fargate or EKS with IAM Roles. Instead of specifying the prefixing related env variables with bottomless IAM access keys through env variables, I think we should rely on Rust SDK so the proper chain can be used automatically. Currently it fails with:

$ sqld --enable-bottomless-replication
..
    LIBSQL_BOTTOMLESS_AWS_DEFAULT_REGION was not set