Fix GeneratorReactor.mapToGenerator()
GeneratorReactor.mapToGenerator() relies on EffectiveStatements having
an identity, as it looks up only based on statement.
Rework the logic to operate on SchemaInferenceStack's state, which
provides hierarchical path which should match Generator layout. This
turns out to be a simple delegator job, but we need to switch matching
strategies when we go along the grouping or augment axis.
JIRA: MDSAL-694
Change-Id: Id87c54fdfc2ff37cdf44503e0603074a74c1c02c
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>