cpanfile: add dependencies of dump_test_schema.pl

The aforementioned script, which is used in the course of patching test
databases, has got two additional dependencies (which in turn depend on
quite a few other new modules), which until now were only mentioned in
a dedicated README file in scripts/ . Put them in the cpanfile where
they belong, wrapped in a dedicated feature so that we do not inflict
them on people who do not want to ever patch test databases.

cpanfile

@@ -26,4 +26,9 @@ requires 'IO::File';
 requires 'POSIX';
 requires 'File::Spec';
 requires 'File::Temp';
-requires 'Time::Piece';
\ No newline at end of file
+requires 'Time::Piece';
+
+feature 'testdb_patcher', 'Additional dependencies of scripts used to patch test databases' => sub {
+  requires 'DBIx::Class::Schema::Loader';
+  requires 'SQL::Translator';
+};