ci: Replace buster with impish for system Qt 5.15.2

Compiler versions:
 - buster: 8.3.0-6
 - impish: 8.5.0-0ubuntu4

Cherry-picked: ea4f68a

Author: hebasto

.cirrus.yml

@@ -225,12 +225,12 @@ task:
 #    FILE_ENV: "./ci/test/00_setup_env_i686_centos.sh"
 
 task:
-  name: '[previous releases, uses qt5 dev package and some depends packages, DEBUG] [unsigned char] [buster]'
+  name: '[previous releases, uses qt5 dev package and some depends packages, DEBUG] [unsigned char] [impish]'
   previous_releases_cache:
     folder: "releases"
   << : *GLOBAL_TASK_TEMPLATE
   container:
-    image: ubuntu:bionic
+    image: ubuntu:impish
   env:
     << : *CIRRUS_EPHEMERAL_WORKER_TEMPLATE_ENV
     FILE_ENV: "./ci/test/00_setup_env_native_qt5.sh"

ci/test/00_setup_env_native_qt5.sh

@@ -7,7 +7,7 @@
 export LC_ALL=C.UTF-8
 
 export CONTAINER_NAME=ci_native_qt5
-export DOCKER_NAME_TAG=debian:buster  # Check that buster gcc-8 can compile our C++17 and run our functional tests in python3, see doc/dependencies.md
+export DOCKER_NAME_TAG=ubuntu:21.10  # Check that impish gcc-8 can compile our C++17 and run our functional tests in python3, see doc/dependencies.md
 export PACKAGES="gcc-8 g++-8 python3-zmq qtbase5-dev qttools5-dev-tools qtdeclarative5-dev qtquickcontrols2-5-dev libdbus-1-dev libharfbuzz-dev"
 export DEP_OPTS="NO_QT=1 NO_UPNP=1 NO_NATPMP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1 CC=gcc-8 CXX=g++-8"
 export TEST_RUNNER_EXTRA="--previous-releases --coverage --extended --exclude feature_dbcrash"  # Run extended tests so that coverage does not fail, but exclude the very slow dbcrash