feat: support timezones in mariadb

Pass timezone info to the runtime container to make MariaDB pick it up:

```bash
$ docker run -it -e "TZ=CET" jbergstroem/mariadb-alpine
```

PR: #266

Dockerfile

@@ -21,7 +21,7 @@ LABEL \
 SHELL ["/bin/ash", "-euo", "pipefail", "-c"]
 
 RUN \
-  apk add --no-cache mariadb=${APK_VERSION} mariadb-client=${APK_VERSION} && \
+  apk add --no-cache "tzdata>=2023c-r1" mariadb=${APK_VERSION} mariadb-client=${APK_VERSION} && \
   TO_KEEP=$(echo " \
     etc/ssl/certs/ca-certificates.crt$ \
     usr/bin/mariadb$ \

test/config.sh

@@ -61,6 +61,15 @@ test_custom_charset_collation() {
   stop "${name}"
 }
 
+test_custom_timezone() {
+  local name="${suite_name}_timezone"
+  ip=$(create "${name}" false "-e SKIP_INNODB=1 -e MYSQL_DATABASE=bar -e TZ=CET")
+  # timezone is set properly
+  ret=$(${CLIENT} -h "${ip}" -N --database=bar -e "SELECT GLOBAL_VALUE FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE VARIABLE_NAME LIKE 'system_time_zone';")
+  assert_equals "CET" "${ret}"
+  stop "${name}"
+}
+
 test_mount_custom_config() {
   local name="${suite_name}_mount_custom_config"
   ip=$(create "${name}" false "-e SKIP_INNODB=1 -v $(pwd)/fixtures/user-my.cnf:/etc/my.cnf.d/my.cnf")