Add option to preserve POSIX metadata

[asaldanha-generate]

When TAR-ing files that are used with FSX or Storage Gateway, or un-TARing files to S3 that may then be used by FSX or Storage Gateway, it would be convenient if POSIX metadata including filetype, permissions, uid and gid could be preserved in the S3 Metadata headers as described in https://docs.aws.amazon.com/fsx/latest/LustreGuide/posix-metadata-support.html. This involves two enhancements

1. When creating an archive with s3tar, S3 Object Metadata is fetched and used to populate the POSIX file type, permissions, uid and gid.

   • x-amz-meta-file-owner is parsed as decimal to set the UID
   • x-amz-meta-file-group parsed as decimal to set the GID
   • x-amz-meta-file-permissions parsed as octal to set the Mode bits

2. Conversely, when extracting a file the TAR header is read prior to creating the object in S3, and

   • x-amz-meta-file-owner is set to the decimal representation of the UID
   • x-amz-meta-file-group is set to the decimal representation of the GID
   • x-amz-meta-file-permissions set to the octal representation of the Mode bits