[16.0][IMP] account_statement_import_online: Pull wizard with dates and one fetch

[pedrobaeza]

This commit improves the provider pull wizard in 2 ways:

• It asks for dates instead of datetimes, as at the end, the minimum pull unit is the whole day, and it was very confusing for the user to select times without knowing that behind the scenes, the whole day will be pulled. Now, the user selects only the day. Quicker and cleaner...
• It includes a check "One fetch", that instructs the pull method to ask to the provider the whole interval in one shot. This way, you don't consume the request rate limits for the providers with them, or only due to speed purposes. It's checked by default, as it's the more natural way of fetching an interval on demand.

@Tecnativa TT55399