Add basictests TAP group and sysbench to CI base image

Part of the CI migration from jenkins-build-scripts to in-repo
test/infra/ infrastructure (#5522). Adds:
- test/tap/groups/basictests/ group (benchmark, chuser, failover tests)
- sysbench to docker-base Dockerfile for benchmark tests

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

test/infra/docker-base/Dockerfile

@@ -24,6 +24,7 @@ RUN apt-get update -qq && \
     python3-yaml \
     python3-packaging \
     python3-structlog \
+    sysbench \
     php-cli \
     php-mysql \
     lcov \

test/tap/groups/basictests/env.sh

@@ -0,0 +1,21 @@
+# Basictests Group Environment
+# Runs Python-based functional tests: sysbench benchmark, change-user, failover.
+# No ProxySQL cluster needed.
+
+export DEFAULT_MYSQL_INFRA="infra-mysql57"
+
+# No cluster
+export SKIP_CLUSTER_START=1
+
+# Test selection
+export TEST_PY_BENCHMARK=1
+export TEST_PY_CHUSER=1
+export TEST_PY_FAILOVER=1
+
+# Disable everything else
+export TEST_PY_INTERNAL=0
+export TEST_PY_STATS=0
+export TEST_PY_TAP=0
+export TEST_PY_TAPINT=0
+export TEST_PY_WARMING=0
+export TEST_PY_READONLY=0

test/tap/groups/basictests/infras.lst

@@ -0,0 +1 @@
+infra-mysql57