Read temporal values from JSON

[alamb]

Note: migrated from original JIRA: https://issues.apache.org/jira/browse/ARROW-4803

Ability to parse strings that look like timestamps to timestamp type. Need to consider whether only timestamp type should be supported as most JSON libraries stick to ISO8601. It might also be inefficient to use regex for timestamps, so the user should provide a hint of which columns to convert to timestamps

[sum12]

It seems the behavior here is not consistent. TemporalValues can get parsed to u64 if they look like u64 otherwise it is a null, but only while dealing with build_struct_array whereas for build_nested_list_array an error is returned.

It could be done as done in csv_reader with regex and extra strings describing possible formats. Or we could have parser as closures (eg : Fn(String) -> Type)) stored in the reader/decoder(/Schema?)

[sum12]

@alamb I would like to take a stab at this one (if it is still relevant)
Thanks for looking :-)

[alamb]

As @nevi-me filed the original ticket, he may have some additional context. Thanks @sum12 !

[tustvold]

Closed by #3835 with further support in #3845