Always convert strings to UTF-8, regardless of column type in SQLite

All columns which would map to a string primitive need this behavior.
Binary has it's own marker type, so it won't go through this conversion.
String and text, which need this, will.

Fixes #18585.

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -50,16 +50,6 @@ def cast_value(value)
       end
     end
 
-    class SQLite3String < Type::String # :nodoc:
-      def type_cast_for_database(value)
-        if value.is_a?(::String) && value.encoding == Encoding::ASCII_8BIT
-          value.encode(Encoding::UTF_8, undef: :replace)
-        else
-          super
-        end
-      end
-    end
-
     # The SQLite3 adapter works SQLite 3.6.16 or newer
     # with the sqlite3-ruby drivers (available as gem from https://rubygems.org/gems/sqlite3).
     #
@@ -239,6 +229,12 @@ def _type_cast(value) # :nodoc:
         case value
         when BigDecimal
           value.to_f
+        when String
+          if value.encoding == Encoding::ASCII_8BIT
+            super(value.encode(Encoding::UTF_8))
+          else
+            super
+          end
         else
           super
         end
@@ -496,7 +492,6 @@ def rename_column(table_name, column_name, new_column_name) #:nodoc:
         def initialize_type_map(m)
           super
           m.register_type(/binary/i, SQLite3Binary.new)
-          register_class_with_limit m, %r(char)i, SQLite3String
         end
 
         def table_structure(table_name)

activerecord/test/cases/adapters/sqlite3/quoting_test.rb

@@ -85,7 +85,7 @@ def quoted_id
 
         def test_quoting_binary_strings
           value = "hello".encode('ascii-8bit')
-          type = SQLite3String.new
+          type = Type::String.new
 
           assert_equal "'hello'", @conn.quote(type.type_cast_for_database(value))
         end