Upgrade CI image to get JDK 16 and Node 14

We need Node 14 to get some Scala.js 1.5.0 tests to pass, but since I
had to regenerate the docker image I also upgraded the JDK to the latest
release.

Author: smarter

.github/workflows/ci.yaml

@@ -28,7 +28,7 @@ jobs:
   test_non_bootstrapped:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2021-03-22
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -49,8 +49,8 @@ jobs:
            && github.repository == 'lampepfl/dotty'
          )"
     steps:
-      - name: Set JDK 15 as default
-        run: echo "/usr/lib/jvm/java-15-openjdk-amd64/bin" >> $GITHUB_PATH
+      - name: Set JDK 16 as default
+        run: echo "/usr/lib/jvm/java-16-openjdk-amd64/bin" >> $GITHUB_PATH
 
       - name: Checkout cleanup script
         uses: actions/checkout@v2
@@ -72,7 +72,7 @@ jobs:
   test:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2021-03-22
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -94,8 +94,8 @@ jobs:
          )"
 
     steps:
-      - name: Set JDK 15 as default
-        run: echo "/usr/lib/jvm/java-15-openjdk-amd64/bin" >> $GITHUB_PATH
+      - name: Set JDK 16 as default
+        run: echo "/usr/lib/jvm/java-16-openjdk-amd64/bin" >> $GITHUB_PATH
 
       - name: Checkout cleanup script
         uses: actions/checkout@v2
@@ -171,7 +171,7 @@ jobs:
   community_build_a:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2021-03-22
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -211,7 +211,7 @@ jobs:
   community_build_b:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2021-03-22
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -251,7 +251,7 @@ jobs:
   test_sbt:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2021-03-22
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -291,7 +291,7 @@ jobs:
   test_java8:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2021-03-22
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -338,7 +338,7 @@ jobs:
   publish_nightly:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2021-03-22
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -373,7 +373,7 @@ jobs:
   nightly_documentation:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2021-03-22
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -415,7 +415,7 @@ jobs:
   publish_release:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2021-03-22
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -498,7 +498,7 @@ jobs:
   release_documentation:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2021-03-22
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -543,7 +543,7 @@ jobs:
   publish_sbt_release:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2021-03-22
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt