Allow disabling of extension loading (through a CMake flag) and allow selectively disabling specific file systems

[Mytherin]

This PR adds support for more granular permission control:

• Support for extension loading and extension installation can be disabled entirely using the -DDISABLE_EXTENSION_LOAD=1 option. When compiled with this option attempting to load or install an external extension (from either remote or from local storage) results in a permission exception.
• Support for specific file systems can be selectively disabled using the disabled_filesystems setting. With this setting we can for example disable the local file system, while keeping support for reading from the remote file system.
  For example:

-- works
SELECT * FROM read_csv_auto('test.csv')
-- disable local file system
SET disabled_filesystems='LocalFileSystem';
-- PermissionException: "LocalFileSystem" has been disabled
SELECT * FROM read_csv_auto('test.csv')
-- works
SELECT * FROM read_csv_auto('https://github.com/duckdb/duckdb/raw/master/data/csv/customer.csv')


-- disable http file system as well
SET disabled_filesystems='LocalFileSystem,HTTPFileSystem';
-- PermissionException: "HTTPFileSystem" has been disabled
SELECT * FROM read_csv_auto('https://github.com/duckdb/duckdb/raw/master/data/csv/customer.csv')

Note that any file system that has previously been disabled cannot be re-enabled without restarting the server (i.e. we can only add to the list of disabled file systems).

[samansmink]

Looks good! No comments on the changes. One thing I noted however is that we have another dlopen for adbc in src/common/adbc/driver_manager.cpp. Not sure if relevant, but should that be stripped too?

[Mytherin]

Looks good! No comments on the changes. One thing I noted however is that we have another dlopen for adbc in src/common/adbc/driver_manager.cpp. Not sure if relevant, but should that be stripped too?

The ADBC code is not accessible through SQL and is only relevant when linking in an ADBC application into the library directly, so that should be fine to leave