The DX is right now pretty terrible:
```
penberg@vonneumann turso % cargo run -- hello.db
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.15s
Running `target/debug/tursodb hello.db`
Turso v0.4.0-pre.18
Enter ".help" for usage hints.
Did you know that Turso supports live materialized views? Type .manual materialized-views to learn more.
This software is in BETA, use caution with production data and ensure you have backups.
turso> PRAGMA journal_mode = 'experimental_mvcc';
× Invalid argument supplied: MVCC is not enabled. Enable it with `--experimental-mvcc` flag in the CLI or by setting the MVCC option in `DatabaseOpts`
turso>
```
To add insult to the injury, many SDKs don't even have a way to enable
MVCC via database options. Therefore, let's remove the flag altogether.
Adds `ALTER TABLE` to the simulator. Currently, there are no properties
that generate `ALTER TABLE`. The query is only generated in
`Property::Query` or in extension queries.
Conditions to generate `ALTER TABLE`:
- In differential testing, do not generate `ALTER COLUMN` as SQLite does
not support it.
- If there is only 1 column, or all columns are present in indexes, do
not generate a `DROP COLUMN` as it would be an error in the database
- if there are no tables, obviously do not generate `ALTER TABLE`
Some fixes:
- handle NULL generation in `GTValue` and `LTValue`, as we now have to
handle nulls due to `ADD COLUMN` adding cols with NULL
- correctly compare NULLs in `binary_compare`
Closes#3650
