Use Cop::Base API for ThreadSafety department

Follow rubocop/rubocop#7868.

The legacy `Cop::Cop` API is soft deprecated and this PR use new `Cop::Base` API instead.

> maintain any RuboCop extensions, as the legacy API will be removed in RuboCop 2.0.

https://metaredux.com/posts/2020/10/21/rubocop-1-0.html

This new API requires RuboCop 0.87 or higher.
https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md#0870-2020-07-06

That dependent version update will be resolved in rubocop#7, so there are no updates in this PR.

lib/rubocop/cop/thread_safety/class_and_module_attributes.rb

@@ -12,7 +12,7 @@ module ThreadSafety
       #   class User
       #     cattr_accessor :current_user
       #   end
-      class ClassAndModuleAttributes < Cop
+      class ClassAndModuleAttributes < Base
         MSG = 'Avoid mutating class and module attributes.'
         RESTRICT_ON_SEND = %i[
           mattr_writer mattr_accessor cattr_writer cattr_accessor

lib/rubocop/cop/thread_safety/instance_variable_in_class_method.rb

@@ -53,7 +53,7 @@ module ThreadSafety
       #
       #     module_function :test
       #   end
-      class InstanceVariableInClassMethod < Cop
+      class InstanceVariableInClassMethod < Base
         MSG = 'Avoid instance variables in class methods.'
         RESTRICT_ON_SEND = %i[
           instance_variable_set
@@ -73,7 +73,7 @@ def on_ivar(node)
           return if method_definition?(node)
           return if synchronized?(node)
 
-          add_offense(node, location: :name, message: MSG)
+          add_offense(node.loc.name, message: MSG)
         end
         alias on_ivasgn on_ivar
 

lib/rubocop/cop/thread_safety/mutable_class_instance_variable.rb

@@ -72,7 +72,8 @@ module ThreadSafety
       #       end
       #     end.freeze
       #   end
-      class MutableClassInstanceVariable < Cop
+      class MutableClassInstanceVariable < Base
+        extend AutoCorrector
         include FrozenStringLiteral
         include ConfigurableEnforcedStyle
 
@@ -108,23 +109,21 @@ def on_masgn(node)
           end
         end
 
-        def autocorrect(node)
+        def autocorrect(corrector, node)
           expr = node.source_range
 
-          lambda do |corrector|
-            splat_value = splat_value(node)
-            if splat_value
-              correct_splat_expansion(corrector, expr, splat_value)
-            elsif node.array_type? && !node.bracketed?
-              corrector.insert_before(expr, '[')
-              corrector.insert_after(expr, ']')
-            elsif requires_parentheses?(node)
-              corrector.insert_before(expr, '(')
-              corrector.insert_after(expr, ')')
-            end
-
-            corrector.insert_after(expr, '.freeze')
+          splat_value = splat_value(node)
+          if splat_value
+            correct_splat_expansion(corrector, expr, splat_value)
+          elsif node.array_type? && !node.bracketed?
+            corrector.insert_before(expr, '[')
+            corrector.insert_after(expr, ']')
+          elsif requires_parentheses?(node)
+            corrector.insert_before(expr, '(')
+            corrector.insert_after(expr, ')')
           end
+
+          corrector.insert_after(expr, '.freeze')
         end
 
         private
@@ -152,15 +151,19 @@ def strict_check(value)
           return if operation_produces_threadsafe_object?(value)
           return if frozen_string_literal?(value)
 
-          add_offense(value)
+          add_offense(value) do |corrector|
+            autocorrect(corrector, value)
+          end
         end
 
         def check(value)
           return unless mutable_literal?(value) ||
                         range_enclosed_in_parentheses?(value)
           return if frozen_string_literal?(value)
 
-          add_offense(value)
+          add_offense(value) do |corrector|
+            autocorrect(corrector, value)
+          end
         end
 
         def in_class?(node)

lib/rubocop/cop/thread_safety/new_thread.rb

@@ -10,7 +10,7 @@ module ThreadSafety
       # @example
       #   # bad
       #   Thread.new { do_work }
-      class NewThread < Cop
+      class NewThread < Base
         MSG = 'Avoid starting new threads.'
         RESTRICT_ON_SEND = %i[new].freeze