Restore binary compatibility for language runtimes generated in 3.1 (to avoid java class verification errors)
FastNodeFinder: support new, SConcept-backed API in addition to legacy, String-backed one.
Generator: switch reflective code to use SConcept/SLanguage instead qualified names
MPS-20980 mps should somehow "interpret" concepts on re-save models action to avoid migration failure: revert deletion of interpreted concept and language runtime. We keep LR to avoid CD hanging in the air, and because there are assumptions about language runtime presence when saving models. Interpreted LR uses interpreted concepts (and behaviors, although implicitly) to avoid tons of errors from IllegalXDescriptor counterparts.
StructureAspectDescriptor.getConceptIds dropped as there were no uses for the method.