Merge branch 'ps/ci-misc-updates'

CI updates (containerization, dropping stale ones, etc.).

* ps/ci-misc-updates:
  ci: remove stale code for Azure Pipelines
  ci: use latest Ubuntu release
  ci: stop special-casing for Ubuntu 16.04
  gitlab-ci: add linux32 job testing against i386
  gitlab-ci: remove the "linux-old" job
  github: simplify computation of the job's distro
  github: convert all Linux jobs to be containerized
  github: adapt containerized jobs to be rootless
  t7422: fix flaky test caused by buffered stdout
  t0060: fix EBUSY in MinGW when setting up runtime prefix

.gitlab-ci.yml

@@ -36,14 +36,11 @@ test:linux:
       fi
   parallel:
     matrix:
-      - jobname: linux-old
-        image: ubuntu:20.04
-        CC: gcc
       - jobname: linux-sha256
-        image: ubuntu:latest
+        image: ubuntu:rolling
         CC: clang
       - jobname: linux-reftable
-        image: ubuntu:latest
+        image: ubuntu:rolling
         CC: clang
       - jobname: linux-breaking-changes
         image: ubuntu:20.04
@@ -53,20 +50,22 @@ test:linux:
         CC: gcc
         CC_PACKAGE: gcc-8
       - jobname: linux-leaks
-        image: ubuntu:latest
+        image: ubuntu:rolling
         CC: gcc
       - jobname: linux-reftable-leaks
-        image: ubuntu:latest
+        image: ubuntu:rolling
         CC: gcc
       - jobname: linux-asan-ubsan
-        image: ubuntu:latest
+        image: ubuntu:rolling
         CC: clang
       - jobname: pedantic
         image: fedora:latest
       - jobname: linux-musl
         image: alpine:latest
+      - jobname: linux32
+        image: i386/ubuntu:20.04
       - jobname: linux-meson
-        image: ubuntu:latest
+        image: ubuntu:rolling
         CC: gcc
   artifacts:
     paths: