- Closes #8111 by making sure that all Excel workbooks are read using a backing file (which should be more memory efficient).
- If the workbook is being opened from an input stream, that stream is materialized to a `Temporary_File`.
- Adds tests fetching Table formats from HTTP.
- Extends `simple-httpbin` with ability to serve files for our tests.
- Ensures that the `Infer` option on `Excel` format also works with streams, if content-type metadata is available (e.g. from HTTP headers).
- Implements a `Temporary_File` facility that can be used to create a temporary file that is deleted once all references to the `Temporary_File` instance are GCed.