nix(refactor): Split memoryTest from tests.nix into memory.nix

nix/memory.nix

@@ -0,0 +1,30 @@
+# The memory tests have large dependencies (a profiled build of PostgREST)
+# and are run less often than the spec tests, so we don't include them in
+# the default test environment. We make them available through a separate module.
+{ buildEnv
+, checkedShellScript
+, curl
+, postgrestProfiled
+, withTools
+}:
+let
+  test =
+    checkedShellScript
+      {
+        name = "postgrest-test-memory";
+        docs = "Run the memory tests.";
+        inRootDir = true;
+      }
+      ''
+        export PATH="${postgrestProfiled}/bin:${curl}/bin:$PATH"
+
+        ${withTools.latest} test/memory-tests.sh
+      '';
+
+in
+buildEnv
+  {
+    name = "postgrest-memory";
+
+    paths = [ test.bin ];
+  } // { bashCompletion = test.bashCompletion; }