Draft: Elastic upgrade: Implement Go Indexer "full" option

What does this MR do and why?

WHAT

• This MR adds logic to do the following
  • Make command to start index processing for Elasticsearch on our Docs content
  • Indexing functionality:
    • Tests connection to Elasticsearch serverless instance
    • Connects to Elasticsearch
    • Only implements INDEX_TYPE=full (goes through all content both English and locale content and creates index mapping with necessary data to support document search).
      • Each mapping will map to a header section (header title and its content) instead of the entire content page (this was our previous implementation).
  • Updates index that is in Elasticsearch instance.

WHY

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Closes #472