Move /src to /subprojects

This will facilitate breaking up Nix into multiple packages for each
component with Meson.

subprojects/perl/t/init.t

@@ -0,0 +1,13 @@
+use strict;
+use warnings;
+use Test2::V0;
+
+use Nix::Store;
+
+my $s = new Nix::Store("dummy://");
+
+my $res = $s->isValidPath("/nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar");
+
+ok(!$res, "should not have path");
+
+done_testing;

subprojects/perl/t/meson.build

@@ -0,0 +1,15 @@
+# Nix-Perl Tests
+#============================================================================
+
+
+# src
+#---------------------------------------------------
+
+nix_perl_tests = files(
+  'init.t',
+)
+
+
+foreach f : nix_perl_tests
+  fs.copyfile(f)
+endforeach