Vendor Elasticsearch 9 templates in the generated gem

[andsel]

Release notes

Vendor ECS template for Elasticsearch 9.x in built gem

What does this PR do?

Update Rakefile to vendor ECS schema template v8 for Elasticsearch 9

Why is it important/What is the impact to the user?

Let the plugin work with Elaticsearch 9 templates

Checklist

• My code follows the style guidelines of this project
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files (and/or docker env variables)
• [ ] I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• vendor and build locally the gem

How to test this PR locally

• vendor the gem

rake vendor
gem build 

• unpack the gem and verify that contains the templates

gem unpack logstash-output-elasticsearch-11.22.9-java.gem
tree logstash-output-elasticsearch-11.22.8-java/lib/logstash/outputs/elasticsearch/templates/

Related issues

• Relates Added template for ES v9 #1187

Use cases

Screenshots

Logs

[WARN ] 2024-09-13 09:54:08.763 [[test2]-pipeline-manager] javapipeline - 'pipeline.ordered' is enabled and is likely less efficient, consider disabling if preserving event order is not necessary
[INFO ] 2024-09-13 09:54:08.766 [Ruby-0-Thread-14: /path/to/logstash-9.0.0-SNAPSHOT/vendor/bundle/jruby/3.1.0/gems/logstash-output-elasticsearch-11.22.8-java/lib/logstash/plugin_mixins/elasticsearch/common.rb:164] elasticsearch - Using a default mapping template {:es_version=>9, :ecs_compatibility=>:v8}
[INFO ] 2024-09-13 09:54:08.766 [Ruby-0-Thread-15: /path/to/logstash-9.0.0-SNAPSHOT/vendor/bundle/jruby/3.1.0/gems/logstash-output-elasticsearch-11.22.8-java/lib/logstash/plugin_mixins/elasticsearch/common.rb:164] elasticsearch - Using a default mapping template {:es_version=>9, :ecs_compatibility=>:v8}
[ERROR] 2024-09-13 09:54:08.766 [Ruby-0-Thread-14: /path/to/logstash-9.0.0-SNAPSHOT/vendor/bundle/jruby/3.1.0/gems/logstash-output-elasticsearch-11.22.8-java/lib/logstash/plugin_mixins/elasticsearch/common.rb:164] 
	elasticsearch - Failed to install template {
		:message=>"Failed to load default template for Elasticsearch v9 with ECS v8; caused by: #<LogStash::ConfigurationError: Failed to load template file '/path/to/logstash-9.0.0-SNAPSHOT/vendor/bundle/jruby/3.1.0/gems/logstash-output-elasticsearch-11.22.8-java/lib/logstash/outputs/elasticsearch/templates/ecs-v8/elasticsearch-9x.json': Template file '/path/to/logstash-9.0.0-SNAPSHOT/vendor/bundle/jruby/3.1.0/gems/logstash-output-elasticsearch-11.22.8-java/lib/logstash/outputs/elasticsearch/templates/ecs-v8/elasticsearch-9x.json' could not be found>", 
		:exception=>LogStash::ConfigurationError, 
		:backtrace=>[
		"/path/to/logstash-9.0.0-SNAPSHOT/vendor/bundle/jruby/3.1.0/gems/logstash-output-elasticsearch-11.22.8-java/lib/logstash/outputs/elasticsearch/template_manager.rb:40:in `load_default_template'", 
		"/path/to/logstash-9.0.0-SNAPSHOT/vendor/bundle/jruby/3.1.0/gems/logstash-output-elasticsearch-11.22.8-java/lib/logstash/outputs/elasticsearch/template_manager.rb:27:in `install_template'", "/path/to/logstash-9.0.0-SNAPSHOT/vendor/bundle/jruby/3.1.0/gems/logstash-output-elasticsearch-11.22.8-java/lib/logstash/outputs/elasticsearch.rb:663:in `install_template'", 
		"/path/to/logstash-9.0.0-SNAPSHOT/vendor/bundle/jruby/3.1.0/gems/logstash-output-elasticsearch-11.22.8-java/lib/logstash/outputs/elasticsearch.rb:371:in `finish_register'", 
		"/path/to/logstash-9.0.0-SNAPSHOT/vendor/bundle/jruby/3.1.0/gems/logstash-output-elasticsearch-11.22.8-java/lib/logstash/outputs/elasticsearch.rb:328:in `block in register'", 
		"/path/to/logstash-9.0.0-SNAPSHOT/vendor/bundle/jruby/3.1.0/gems/logstash-output-elasticsearch-11.22.8-java/lib/logstash/plugin_mixins/elasticsearch/common.rb:172:in `block in after_successful_connection'"
		]
	}

https://buildkite.com/elastic/logstash-pull-request-pipeline/builds/1457#0191e54c-3934-4a5d-a1df-636cbe9358df/2224-2521