Nicer diff interface in intent handlers

[shlomi-nx]

Get rid of the second-level nested array in diffs unless the diff type is actually an array (e.g. spec[0].diff[0] when diffing two strings)

• It's confused me and everyone else I know who's had to learn it
• It makes provider code harder to read / leads to smelly code (e.g. "why is [0] always hardcoded for the nested array?")

Some design is needed

It may be difficult to embed the schema in the differ itself, perhaps we need a second pass on the differ results which will run against the schema and flatten unneeded vectors.