Incorporate support for dropping foreign keys in SQLite when available

[boris-kolpackov]

Currently (as of version 3.53.0) SQLite does not support dropping of foreign key constraints which in turn means one cannot drop columns that belong to such constraints. Which makes the now support ALTER TABLE DROP COLUMN quite limited. On our side this means we have to still resort to logical drop (set to NULL) for such columns.

But it feels like this support might be coming soon and so we should check future SQLite versions: https://sqlite.org/forum/forumpost/ac8e024cdd