Previous approach for property reconfiguration was to create a free-floating map with generalized representations of all fields. This patch does it right.

When property is reconfigured either by changing its kind (kData <-> kAccessor) or its attributes it implies creation of a new branch in transition tree. If such a branch already existed before reconfiguration then it should be merged with the old (or source) branch of the transition tree. Merging procedure includes all the heavy machinery such as property location changes (kDescriptor -> kField), field representation/field type generalization, map deprecation, etc.

Review URL: https://codereview.chromium.org/888623002

Cr-Commit-Position: refs/heads/master@{#26667}