feat(s3): support default credentials provider in AWS S3 storage

[rohilsurana]

Problem

Currently the only way to set AWS credentials is via setting the static credentials as environment variables or by passing as a flag when executing.
Some systems already have credentials setup using different ways provided by aws like credentials file, config file or EC2 profiles.

Solution

This PR adds support for using AWS S3 credentials from default credentials provider chain in the SDK.
The order for the AWS SDK golang is documented at [1].
The order for duckdb is documented at [2].

Changes

• Adds a new configuration AWS_CREDENTIALS_TYPE with options STATIC and DEFAULT.
  • STATIC maintains the old behaviour and uses the supplied static credentials.
  • DEFAULT uses the AWS SDK and DuckDB default credentials chain.
• AWS client config changes for syncing tables
• DuckDB create secret query changes for creating S3 secret as per new config.
• Update README with details of the new config.

[1] AWS SDK Golang - https://docs.aws.amazon.com/sdk-for-go/v1/developer-guide/configuring-sdk.html#specifying-credentials
[2] DuckDB S3 API Support - https://duckdb.org/docs/extensions/httpfs/s3api.html#credential_chain-provider