ST6RI-795 Improve performance of validation involving inherited memberships

[seidewitz]

This PR implements performance improvements for the computation of the inherited memberships of a namespace, primarily in a set of methods in the TypeAdapter.

Through performance profiling, it was determined that the time spent doing validation was dominated by validation checks on namespaces, functions and expressions that required the computation of inherited members. In addition, some of the most time-expensive transformations also required this computation, in order to get the inherited ends of connectors and connection usages. Improving the performance of the inheritance computation was thus seen to have a potentially high impact.

Further analysis indicated that the major performance cost in the inheritance computation was in removing memberships due to redefinition relationships. Two major changes were implemented to address this:

1. The removal of redefined features is now handled incrementally as the specialization graph is traversed to collect inherited memberships, rather than by a second pass run after a initial set of memberships is collected. (This is similar to the approach used to handle redefinition for name resolutions in KerMLScope.)
2. As the indirectly redefined features are determined for particular redefining features and for all the features in a type, this information is cached so it does not have to be recomputed subsequently as the specialization graph is traversed (or in subsequent inheritance computations).

As a result of these changes, the processing time for larger models can be reduced by half or more.