Make S3FileSystemFactory use configured AWS access keys for STS calls

[grantatspothero]

Description

S3FileSystemFactory STSClient does not use the trino configured AWS access key/secret to connect to STS.

This is an [unintentional] change in behavior from TrinoS3Filesystem which uses the configured trino AWS access key/secret to connect to STS.

Additional context and related issues

I was able to manually test this fix locally by:

• creating an AWS user with permissions to assume a role, but no other permissions
• creating a role with permissions to read/write to an s3 bucket
• configuring the iceberg connector to use the native-s3 filesystem with the above user access credentials and role and then successfully reading/writing tables to the s3 bucket

Release notes

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# Section
* Fix some things. ({issue}`issuenumber`)