chore(ci): update ci image to new 2023-06-21 tag

This makes a few changes that we'll test out:

1. All the places where 16 was the default JDK version will now be set
   to 17.
2. All images will be the same and set to 2023-06-21
3. For now, the community build will remain on 8, but I'll attempt to
   bump that separately after this all works.

Author: ckipp01

.github/workflows/ci.yaml

@@ -45,7 +45,7 @@ jobs:
   test_non_bootstrapped:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2021-03-22
+      image: lampepfl/dotty:2023-06-21
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -63,9 +63,6 @@ jobs:
            && github.repository == 'lampepfl/dotty'
          )"
     steps:
-      - name: Set JDK 16 as default
-        run: echo "/usr/lib/jvm/java-16-openjdk-amd64/bin" >> $GITHUB_PATH
-
       - name: Reset existing repo
         run: git -c "http.https://github.com/.extraheader=" fetch --recurse-submodules=no "https://github.com/lampepfl/dotty" && git reset --hard FETCH_HEAD || true
 
@@ -94,7 +91,7 @@ jobs:
   test:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2021-03-22
+      image: lampepfl/dotty:2023-06-21
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -114,9 +111,6 @@ jobs:
          )"
 
     steps:
-      - name: Set JDK 16 as default
-        run: echo "/usr/lib/jvm/java-16-openjdk-amd64/bin" >> $GITHUB_PATH
-
       - name: Reset existing repo
         run: git -c "http.https://github.com/.extraheader=" fetch --recurse-submodules=no "https://github.com/lampepfl/dotty" && git reset --hard FETCH_HEAD || true
 
@@ -217,7 +211,7 @@ jobs:
     name: MiMa
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2021-03-22
+      image: lampepfl/dotty:2023-06-21
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -258,7 +252,7 @@ jobs:
   community_build_a:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2021-03-22
+      image: lampepfl/dotty:2023-06-21
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -279,6 +273,9 @@ jobs:
          )"
 
     steps:
+      - name: Set JDK 8 as default
+        run: echo "/usr/lib/jvm/java-8-openjdk-amd64/bin" >> $GITHUB_PATH
+
       - name: Reset existing repo
         run: git -c "http.https://github.com/.extraheader=" fetch --recurse-submodules=no "https://github.com/lampepfl/dotty" && git reset --hard FETCH_HEAD || true
 
@@ -307,7 +304,7 @@ jobs:
   community_build_b:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2021-03-22
+      image: lampepfl/dotty:2023-06-21
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -328,6 +325,9 @@ jobs:
          )"
 
     steps:
+      - name: Set JDK 8 as default
+        run: echo "/usr/lib/jvm/java-8-openjdk-amd64/bin" >> $GITHUB_PATH
+
       - name: Reset existing repo
         run: git -c "http.https://github.com/.extraheader=" fetch --recurse-submodules=no "https://github.com/lampepfl/dotty" && git reset --hard FETCH_HEAD || true
 
@@ -356,7 +356,7 @@ jobs:
   community_build_c:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2020-11-19
+      image: lampepfl/dotty:2023-06-21
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -377,6 +377,9 @@ jobs:
          )"
 
     steps:
+      - name: Set JDK 8 as default
+        run: echo "/usr/lib/jvm/java-8-openjdk-amd64/bin" >> $GITHUB_PATH
+
       - name: Reset existing repo
         run: git -c "http.https://github.com/.extraheader=" fetch --recurse-submodules=no "https://github.com/lampepfl/dotty" && git reset --hard FETCH_HEAD || true
 
@@ -405,7 +408,7 @@ jobs:
   test_sbt:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2021-03-22
+      image: lampepfl/dotty:2023-06-21
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -445,7 +448,7 @@ jobs:
   test_java8:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2021-03-22
+      image: lampepfl/dotty:2023-06-21
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -499,7 +502,7 @@ jobs:
   publish_nightly:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2021-03-22
+      image: lampepfl/dotty:2023-06-21
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -550,7 +553,7 @@ jobs:
   nightly_documentation:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2021-03-22
+      image: lampepfl/dotty:2023-06-21
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -601,7 +604,7 @@ jobs:
       contents: write  # for actions/create-release to create a release
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2021-03-22
+      image: lampepfl/dotty:2023-06-21
       options: --cpu-shares 4096
       volumes:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
@@ -689,7 +692,7 @@ jobs:
   open_issue_on_failure:
     runs-on: [self-hosted, Linux]
     container:
-      image: lampepfl/dotty:2021-03-22
+      image: lampepfl/dotty:2023-06-21
     needs: [nightly_documentation, test_windows_full]
     # The `failure()` expression is true iff at least one of the dependencies
     # of this job (including transitive dependencies) has failed.