(MODULES-11244) fix changelog generation

* save existing changelog to HISTORY.md
* configure changelog generator to generate new entries
    starting with 4.9.0 tag
* pin octokit to 4.21.0 since we hit the issue at octokit/octokit.rb#1391
* pin async to ~> 1.30 otherwise async 2.0.0(needs ruby >=3.1.0) is wrongly selected by
    bundler on jenkins while running with ruby 2.7.1

Author: Ciprian Badescu

.sync.yml

@@ -36,6 +36,10 @@ Gemfile:
       - gem: 'beaker-task_helper'
         version: '~> 1.9'
         condition: 'ENV["GEM_BOLT"]'
+      - gem: octokit
+        version: '4.21.0' # due to https://github.com/octokit/octokit.rb/issues/1391
+      - gem: async
+        version: '~> 1.30' # otherwise async 2.0.0(needs ruby >=3.1.0) is wrongly selected by bundler on jenkins while running with ruby 2.7.1
 appveyor.yml:
   delete: true
 .travis.yml:
@@ -50,3 +54,5 @@ spec/default_facts.yml:
   delete: true
 spec/spec_helper.rb:
   unmanaged: true
+Rakefile:
+  changelog_since_tag: 4.9.0

Gemfile

@@ -37,6 +37,8 @@ group :development do
   gem "nokogiri",                                                                require: false
   gem "bolt", '~> 3.0',                                                          require: false if ENV["GEM_BOLT"]
   gem "beaker-task_helper", '~> 1.9',                                            require: false if ENV["GEM_BOLT"]
+  gem "octokit", '4.21.0',                                                       require: false
+  gem "async", '~> 1.30',                                                        require: false
 end
 group :system_tests do
   gem "puppet-module-posix-system-r#{minor_version}", '~> 1.0', require: false, platforms: [:ruby]