Cache packages' dependencies

[AlexRuiz7]

Description

The packages' builder downloads the required dependencies, such as the OpenSearch plugins, on each run, considerably slowing down its execution. The process can be fastened by caching these dependencies on GH Workflow.

The goal of this issue is to reuse these dependencies on each run, as they only change when we move to a different version of OpenSearch.

Functional requirements

• The packages builder workflow caches OpenSearch plugins by version.
• The packages builder workflow uses the cache to speed up the building (does not download the plugins on each run, unless required).
• The process to manage cache entries is documented, describing when and how cache entries should be deleted.

Implementation restrictions

• GH Workflow cache mechanism must be used.
• Workflow inputs must not change.
• Workflow executions using cache must be faster than those not using cache.

Plan

• Update the build.yml workflow to cache OpenSearch plugins
• Update the build.yml workflow to install OpenSearch plugins from cache, if it exists.
• Create a Cache Management User Manual, describing when cache entries are considered obsolete and how they can be deleted.