JavaScript: Consolidate Express tests.

Instead of having many small independent tests, we now just have a single test that pulls in all the individual tests and runs them together.

Concretely, each `.ql` file has been turned into a `.qll` file with a query predicate corresponding to the original `select` clause and named after the original `.ql` file, plus a prefix `test_`.

The newly added `tests.ql` imports all these `.qll`s.

The individual `.expected` files have been concatenated together into `tests.expected`, each prefixed with the name of the corresponding query predicate. (This is the format that qltest produces for tests with multiple query predicates.)

Author: Max Schaefer

javascript/ql/test/library-tests/frameworks/Express/CookieMiddlewareInstance.expected

@@ -0,0 +1,6 @@
+import javascript
+
+query
+predicate test_CookieMiddlewareInstance(HTTP::CookieMiddlewareInstance instance, DataFlow::Node res) {
+  res = instance.getASecretKey()
+}

javascript/ql/test/library-tests/frameworks/Express/CookieMiddlewareInstance.ql

@@ -0,0 +1,5 @@
+import javascript
+
+query predicate test_Credentials(Express::Credentials cr, string res) {
+  res = cr.getCredentialsKind()
+}

javascript/ql/test/library-tests/frameworks/Express/CookieMiddlewareInstance.qll

@@ -0,0 +1,8 @@
+import javascript
+import semmle.javascript.frameworks.ExpressModules
+
+query
+predicate test_ExpressSession(ExpressLibraries::ExpressSession::MiddlewareInstance session,
+                              string name, DataFlow::Node res) {
+  res = session.getOption(name)
+}