feat: Handle S3 region

[NickLarsenNZ]

Description

Part of stackabletech/issues#696.

Note

S3a seems to do some region parsing from the URL instead of leaving it to the AWS SDK (if I interpreted the docs correctly).
See:

• https://hadoop.apache.org/docs/r3.4.1/hadoop-aws/tools/hadoop-aws/connecting.html#Region_and_endpoints_misconfigured
• https://hadoop.apache.org/docs/r3.4.1/hadoop-aws/tools/hadoop-aws/third_party_stores.html

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[NickLarsenNZ]

Is this ok as is, since it is a BTreeMap<String, Option<String>> (ie, V = Option<_>). Or do we want to make it like this:

if let Some(region_name) = s3.region.name() {
  data.insert(
    MetaStoreConfig::S3_REGION_NAME.to_string(),
    Some(region_name.to_string()),
  );
}