Fix 4714 postgresql alter column nullability

[griffio]

fixes #4714

🚧 🍔 🏗️ PR to try and fix TableInterfaceGenerator for PostgreSql Dialect

The AlterColumn Mixin will set the QueryColumn to appropriate nullable flag and this can be read in TableInterfaceGenerator

As we can't modify ColumnDefs, use the QueryColumn to override the not null/nullable type if it is true or false (normally the nullable property will be null so no impact)

🦺 Migration Test case to show it works

Have tried locally with snapshot build 📸

four fields - drop and set nullability on y, t - keep a, b the same as a control

1.sqm

CREATE TABLE X(
    y INTEGER NOT NULL,
    t TEXT,
    a INTEGER NOT NULL,
    b TEXT
);

                 Table "public.x"
 Column |  Type   | Collation | Nullable | Default
--------+---------+-----------+----------+---------
 y      | integer |           | not null |
 t      | text    |           |          |
 a      | integer |           | not null |
 b      | text    |           |          |

public data class X(
  public val y: Int,
  public val t: String?,
  public val a: Int,
  public val b: String?,
)

public class XQueries(
  driver: SqlDriver,
) : TransacterImpl(driver) {
  public fun insertX(
    y: Int,
    t: String?,
    a: Int,
    b: String?,
  ) 

2.sqm

ALTER TABLE X
ALTER COLUMN y DROP NOT NULL;

ALTER TABLE X
ALTER COLUMN t SET NOT NULL;

After:

public data class X(
  public val y: Int?,
  public val t: String,
  public val a: Int,
  public val b: String?,
)

public class XQueries(
  driver: SqlDriver,
) : TransacterImpl(driver) {
  public fun insertX(
    y: Int?,
    t: String,
    a: Int,
    b: String?,
  ) 

                 Table "public.x"
 Column |  Type   | Collation | Nullable | Default
--------+---------+-----------+----------+---------
 y      | integer |           |          |
 t      | text    |           | not null |
 a      | integer |           | not null |
 b      | text    |           |          |