Added InferDictionariesFromRecords flag to JSON TP

[nikoyak]

JSON TP always projects json record fields into the properties of generated types. Sometimes it is not desirable. The added flag will allow to infer dictionaries from the records if the names of all the fields of similar records in the provider's training data are inferred to the same non-string primitive type (by type inference rules). The flag is not set by default for backwards compatibility.

The current implementation makes it meaningless to process such data in the JSON Provider:

{ "sales": { "2022-01-13": { "count": 3 }, "2022-01-23": { "count": 5 }, "2022-01-28": { "count": 4 }, "2022-02-01": { "count": 5 }, "2022-02-07": { "count": 1 }, "2022-02-13": { "count": 2 } } }

With this PR, for example, it is easy to find out from the above data how many sales were in February:

type TP = JsonProvider<"""{ "sales": { "1970-01-01": { "count": 100 }}}""", InferDictionariesFromRecords = true>
let s = """{ "sales": { "2022-01-13": { "count": 3 }, "2022-01-23": { "count": 5 }, "2022-01-28": { "count": 4 }, "2022-02-01": { "count": 5 }, "2022-02-07": { "count": 1 }, "2022-02-13": { "count": 2 } } }"""
TP.Parse(s).Sales.Items
|> Seq.filter (fun (k, _) -> k.Month = 2)
|> Seq.sumBy (fun (_, v) -> v.Count)

In addition to the Items: (InferedKey * InferedValue) seq property specified in the code above, the generated dictionary-like type contains the Count, IsEmpty, Keys, Values properties, the Item indexed property, and the ContainsKey, TryFind methods, similar to the members of FSharp.Collections.Map

[dsyme]

Suggest PreferDictionaries instead of InferDictionariesFromRecords

[dsyme]

I left a couple of suggestions, but otherwise marked as approved, the code looks great

[nikoyak]

done

[cartermp]

Thanks!