Cosmos: allow value converters for collections of primitive types

[AndriySvyryd]

See https://github.com/npgsql/efcore.pg/blob/main/src/EFCore.PG/Storage/ValueConversion/INpgsqlArrayConverter.cs for a way of implementing this.

Also try to use built-in converters automatically, see https://github.com/npgsql/efcore.pg/blob/main/src/EFCore.PG/Storage/ValueConversion/NpgsqlValueConverterSelector.cs

[ajcvickers]

Note from triage: also consider other issues related to primitive collections--see label area-primitive-collections.

[ajcvickers]

Note for team: either a duplicate of #4179, or already supported if the issue means using value converters explicitly.