Allow extensions to contribute datasouces

Making this build item public should allow extension to contribute extensions
at build time. This allows the possiblity of defining datasources as code rather
than config.

Runtime attributes still need to be provided as config, however it is already possible
for extensions to provide runtime config so this is not really a concern.

extensions/agroal/deployment/src/main/java/io/quarkus/agroal/deployment/AggregatedDataSourceBuildTimeConfigBuildItem.java

@@ -5,7 +5,7 @@
 import io.quarkus.datasource.common.runtime.DataSourceUtil;
 import io.quarkus.datasource.runtime.DataSourceBuildTimeConfig;
 
-final class AggregatedDataSourceBuildTimeConfigBuildItem extends MultiBuildItem {
+public final class AggregatedDataSourceBuildTimeConfigBuildItem extends MultiBuildItem {
 
     private final String name;
 
@@ -17,7 +17,7 @@ final class AggregatedDataSourceBuildTimeConfigBuildItem extends MultiBuildItem
 
     private final String resolvedDriverClass;
 
-    AggregatedDataSourceBuildTimeConfigBuildItem(String name, DataSourceBuildTimeConfig dataSourceConfig,
+    public AggregatedDataSourceBuildTimeConfigBuildItem(String name, DataSourceBuildTimeConfig dataSourceConfig,
             DataSourceJdbcBuildTimeConfig jdbcConfig,
             String dbKind,
             String resolvedDriverClass) {