BOLT-1048: Add dedicated OpenADR XML codec test files

Artem asked in Slack thread 1779825963.485559 / message 1779875559.558239 to create two tests for two files from the already-merged BOLT-1048-OpenADR-XML-codec--parser-builder branch and open a new MR/PR. Scope: test-only follow-up against main. Add new dedicated test files for OpenADR XML codec files, run targeted tests + adapters/program lint, open PR linked to BOLT-1048, monitor CI.