R1:28a24c333fdd

Fix a couple of other missing getApplicationTransactionCommentObject() implementations

Summary:
See PHI165. See D18715. These objects (projects, blogs) also need implementations now.

(I thought about making this method `abstract` or doing try/catch to maybe make this more robust, but I think this should be the end of it, and those changes have mild complexity/compatibility/risk issues.)

Test Plan: Changed `bin/search index` to index only one document of each type, ran `bin/search index --all --force`…