Store all sequences in one annotation #14103
Description
If the sequence annotation has a constant name and contains all enums and the inner collection is a dictionary with (name, schema) as the key then the lookup will be faster as you don't need to go through all the annotations and don't need to allocate a new string.
Even though this is not that important for ISequence in particular, since it's only used in migrations it provides an example to other providers that could be an anti-pattern.
Also sequences should be stored as Fluent API in the migration snapshot with compatibility mode for the old format.