BOLT-1048: Add second pair of focused OpenADR XML codec tests

Artem clarified in Slack thread 1779949844.079209 / message 1779996781.304789 that PR #11210 covered the previous two files, and he wants a new PR for two different files changed by BOLT-1048-OpenADR-XML-codec--parser-builder (PR #11143). Scope: test-only follow-up against main; add two new dedicated test files for different OpenADR XML codec files, validate locally, open PR linked to BOLT-1048, monitor CI.