Temporal table migrations refactor.

[maumar]

Before we used to put temporal annotations on temporal tables and all their columns, so that it's easier to process. Problem was that this would generate very noisy migrations when converting from regular table to temporal and vice versa. Every column would have an AlterColumn operation (which we would ignore during processing, but they were nonetheless generated in migration files). Also, we were using relatively simple logic to track state of our temporal tables. Some operations require temporary disabling of the versioning/period, and we need to keep track of that so that we don't try to disable period twice, or forget to enable it later. The way we did it could lead to invalid SQL in some non-trivial scenarios (e.g. converting table to temporal and adding a new column at the same time)

The new approach is to only put temporal annotations on the table itself, and the period columns. Regular columns of the temporal table don't have any temporal annotations on them anymore and we reason about temporal information based on other table-based migration operation in the batch and, if need be, on the relational model. We also keep track of the actual temporal information for every operation (rather than keeping global dictionaries of period/version), so that complex migrations, involving multiple operations are more robust. To achieve that we compute the initial (temporal) state of all the tables involved in the migration. We scan all the table operations, and if some info is missing we get it from relational model. Then we do the proper processing of the migration operations - when we encounter table operation, we update the temporal information for that table (since table operations contain relevant temporal annotations). For all other operations we extract the current temporal state for the table involved, and reason based on that info.

Fixes #27459 - SQL Server Migrations: Review temporal table annotations
Fixes #29536 - EF Core IsTemporal() creates huge migration
Fixes #29799 - EF7 SqlServer Migration is trying to update columns on History table before creating the History table if any new columns are added in the same migration

[bricelam]

LGTM. Just need to test scenarios with existing migrations.