Add `--absolute` parameter to `aws s3 ls`

The `--absolute` flag would cause the displayed matches to show the absolute key rather than a truncated key with the prefix missing.

```
$aws s3 ls foo/bar --recursive
bar/baz
bar/buz

```

```
$aws s3 ls foo/bar --recursive --absolute
foo/bar/baz
foo/bar/buz

```

Start at the `aws s3 ls` command entry point and trace how recursive matches are formatted when a prefix is supplied. Run the examples from the issue to confirm the current truncated output. Done means `--absolute` preserves the full prefix in each displayed key while existing output remains unchanged without the flag.

Written by the indexing model from the issue text.