Update GitHub actions and fix codecov.

Author: renggli

.github/workflows/dart.yml

@@ -16,11 +16,11 @@ jobs:
     name: "Dart CI"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/cache@v3
+      - uses: actions/cache@v4
         with:
           path: "~/.pub-cache/hosted"
           key: "os:ubuntu-latest;pub-cache-hosted;dart:stable"
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: dart-lang/setup-dart@v1
       - name: "Dependencies"
         run: dart pub upgrade --no-precompile
@@ -37,12 +37,14 @@ jobs:
           dart pub global activate coverage
           dart pub global run coverage:test_with_coverage --test test/all_test.dart
       - name: "Upload coverage"
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
   check:
     name: "Flutter CI"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: amake/dart-flutter-compat@v1
         with:
           channel: stable