change_column_null re-declares a datetime2(n) column as datetime(n), which SQL Server refuses #1417

Description

change_column_null rebuilds the column type from the column's abstract type:

# lib/active_record/connection_adapters/sqlserver/schema_statements.rb
sql = "ALTER TABLE #{table_id} ALTER COLUMN #{column_id} #{type_to_sql column.type, limit: column.limit, precision: column.precision, scale: column.scale}"

For a column created as :datetime with a precision, the adapter makes a datetime2(n) column, and that rule
is applied in TableDefinition#new_column_definition and in change_column
(type = :datetime2 unless options[:precision].nil?). But change_column_null calls type_to_sql directly:
the column's type is :datetime and its precision is 6, so the statement says datetime(6):

ALTER TABLE [events] ALTER COLUMN [at] datetime(6) NOT NULL
TinyTds::Error: Column, parameter, or variable #4: Cannot specify a column width on data type datetime.

Steps to reproduce

activerecord-sqlserver-adapter 8.0.10, Rails 8.0 (the method is the same on main):

connection.create_table(:events) { |t| t.column :at, :datetime, precision: 6 }
connection.columns(:events).find { |c| c.name == "at" }.sql_type # => "datetime2(6)"
connection.change_column_null(:events, :at, false)
# => ActiveRecord::StatementInvalid: TinyTds::Error: ... Cannot specify a column width on data type datetime.

Expected

ALTER TABLE [events] ALTER COLUMN [at] datetime2(6) NOT NULL

Suggested fix

Apply the same rule where the type is turned into SQL, so every caller gets it — e.g. in type_to_sql:

def type_to_sql(type, limit: nil, precision: nil, scale: nil, **)
  type = :datetime2 if type.to_s == "datetime" && !precision.nil?
  # ...
end

or map the type in change_column_null the way change_column does.