feature: implement setTimeout, setInterval, clearTimeout, and clearInterval

Using the new fastly_async_io module we can implement JS timers 🥳

This pull-request implements setTimeout, setInterval, clearTimeout, and clearInterval and adds some interface and basic tests for them.
There are also tests in the web-platform-tests that exercise the functions fully, which is why I only needed to write some basic tests.

Author: dependabot[bot]

.github/workflows/main.yml

@@ -381,3 +381,14 @@ jobs:
       with:
         fixture: 'status'
         fastly-api-token: ${{ secrets.FASTLY_API_TOKEN }}
+  e2e-timers:
+    runs-on: ubuntu-latest
+    needs: [build]
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        submodules: false
+    - uses: ./.github/actions/e2e
+      with:
+        fixture: 'timers'
+        fastly-api-token: ${{ secrets.FASTLY_API_TOKEN }}

.vscode/settings.json

@@ -84,7 +84,10 @@
         "__tree": "cpp",
         "charconv": "cpp",
         "list": "cpp",
-        "regex": "cpp"
+        "regex": "cpp",
+        "__functional_03": "cpp",
+        "__functional_base_03": "cpp",
+        "memory_resource": "cpp"
     },
     "git.ignoreLimitWarning": true
 }