Run the upstream test262 tests

The Temporal test262 tests are being removed from tc39/proposal-temporal
(see tc39/proposal-temporal#1853 ) and moved
to tc39/test262 where they will continue to be developed. Run them from a
git submodule so we can pull in new upstream versions when we are ready
for them.

Instead of cloning tc39/proposal-temporal to run the tests, we copy the
relevant parts of its test262 CI script. The files expected-failures.txt,
parseResults.js, and preprocessor.test262.cjs are copied from there as
well.

.github/workflows/test.yml

@@ -29,6 +29,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
+      with:
+        submodules: true
     - name: use node.js v16.x
       uses: actions/setup-node@v1
       with:

.gitignore

@@ -5,4 +5,3 @@ tsc-out/
 .vscode/*
 !.vscode/launch.json
 *.tgz
-test/tc39

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "test262"]
+	path = test262
+	url = https://github.com/tc39/test262