DuckDB: sniff_csv provides filesystem access even when enable_external_access is disabled

DuckDB is a SQL database management system. In versions 1.0.0 and prior, content in filesystem is accessible for reading using `sniff_csv`, even with `enable_external_access=false`. This vulnerability provides an attacker with access to filesystem even when access is expected to be disabled and other similar functions do NOT provide access. There seem to be two vectors to this vulnerability. First, access to files that should otherwise not be allowed. Second, the content from a file can be read (e.g. `/etc/hosts`, `proc/self/environ`, etc) even though that doesn't seem to be the intent of the sniff_csv function. A fix for this issue is available in commit c9b7c98aa0e1cd7363fe8bb8543a95f38e980d8a and is expected to be part of version 1.1.0.