Modular clinical domain profiles and table1_generator()

A profile bundles labs / vitals (LOINC), medication classes (ATC codes resolved through concept + concept_ancestor) and comorbidities (ICD-10 code prefixes on condition_source_value) for a clinical domain. The built-in profiles live in inst/extdata/domain_profiles.yml (shared with the Python omop_etl.DOMAIN_PROFILES). They are a starting point for review by a clinician of that domain, not a validated specification.