improve missing properties type error

[nnullcolumn]

before:
Table type '{ cafood: string, tag: "cat" }' not compatible with type 'Cat' because the former is missing field 'catfood'
after:
required field 'catfood' not found in type '{ cafood: string, tag: "cat" }' from expected type 'Cat'

before:
Table type '{| x: number, y: number |}' not compatible with type 'Super' because the former has extra field 'y'
after:
extra field 'y' found in type '{| x: number, y: number |}' from expected type 'Super'

• ran clang-format on changed files, fixed an old issue or two
• closes List missing properties *before* the stringified table type in TypeError messages #2097
• updated tests

[hgoldstein]

Looks great! However, even "less critical" changes like this should be flagged.