Add data model analysis

[anngvu]

Add analysis of data model changes in each PR that:

1. Identifies the number of/which manifest templates affected by this change.
2. Summarizes when keys may collide across files when schematic converts everything to uppercase (i.e. in the final output there is no distinguishing keys that were originally meningioma vs Meningioma in the source), which can lead to bugs. Also, when editing YAML in most code editors, using a duplicate key under the same parent is clearly pointed out, but duplicate keys can still happen across files. See ID collision for two entities MPNST and menigioma #450.
3. Summarizes changes in numbers of props, classes, and enums.

The first is relevant for #312.