- SERIAL and BIGSERIAL are not true types and can't be used in ALTER TABLE expressions
- When changing between int and bigint auto increment fields the default should no be dropped
  to preserve the link between the column and the sequence.

As per @belgattitude's review.

Since the test is skipped when the driver is not an instance of
`VersionAwarePlatformDriver` we don't need to validate it again.

The message was a bit confusing as well (expected vs given).

Since the JSON type is simply an alias to a LONG TEXT we must force
a comment, otherwise things will not work properly.

Also the test for JSON types should work regardless of native JSON
support (DBAL should add a comment to identify the correct type).

Unescaping re-added, support limited to schema introspection (#2850 will bring more complete coverage)

Postgres has a `SERIAL` data type to allow shorthand for
`nextval('sequence_name')`, but DDL like this:

    CREATE TABLE example (id SERIAL)

Cannot be generated in the DBAL schema APIs.

And then we don't need to wait till v3 to not require comments on the
JsonType.

On 31d01283 we made JsonType the default
one, which caused some unexpected results with the comparator.

This tests validates that if users have a JSON column but are using the
JsonArrayType we'll just add a comment to the column.

Reference: https://github.com/doctrine/dbal/pull/2782

statements in a rewindable iterator. Skipped the test for iterating
multiple times with a message regarding that iterators are non
rewindable.

Only added to mysqli for now, can add to other drivers (assuming they
support reseting the pointer in some way) after feedback.

Test fails because it's not possible to reuse a generator in this way.