Move extract_scale to decimal type

The only type that has a scale is decimal. There's a special case where
decimal columns with 0 scale are type cast to integers if the scale is
not specified. Appears to only affect schema dumping.

activerecord/lib/active_record/connection_adapters/type.rb

@@ -22,8 +22,8 @@ module ActiveRecord
       class << self
         def extract_scale(sql_type)
           case sql_type
-            when /^(numeric|decimal|number)\((\d+)\)/i then 0
-            when /^(numeric|decimal|number)\((\d+)(,(\d+))\)/i then $4.to_i
+            when /\((\d+)\)/ then 0
+            when /\((\d+)(,(\d+))\)/ then $3.to_i
           end
         end
       end

activerecord/lib/active_record/connection_adapters/type/decimal.rb

@@ -4,6 +4,8 @@ module ActiveRecord
       class Decimal < Value # :nodoc:
         include Numeric
 
+        delegate :extract_scale, to: Type
+
         def type
           :decimal
         end

activerecord/lib/active_record/connection_adapters/type/value.rb

@@ -3,10 +3,7 @@ module ActiveRecord
     module Type
       class Value # :nodoc:
         def type; end
-
-        def extract_scale(sql_type)
-          Type.extract_scale(sql_type)
-        end
+        def extract_scale(sql_type); end
 
         def type_cast(value)
           cast_value(value) unless value.nil?

activerecord/test/cases/schema_dumper_test.rb

@@ -353,9 +353,9 @@ class SchemaDumperTest < ActiveRecord::TestCase
     output = standard_dump
     # Oracle supports precision up to 38 and it identifies decimals with scale 0 as integers
     if current_adapter?(:OracleAdapter)
-      assert_match %r{t.integer\s+"atoms_in_universe",\s+precision: 38,\s+scale: 0}, output
+      assert_match %r{t.integer\s+"atoms_in_universe",\s+precision: 38}, output
     else
-      assert_match %r{t.decimal\s+"atoms_in_universe",\s+precision: 55,\s+scale: 0}, output
+      assert_match %r{t.decimal\s+"atoms_in_universe",\s+precision: 55}, output
     end
   end