[DOC] Grok processor supports capture_all_matches option

[gaobinlong]

What do you want to do?

• Add new documentation

Tell us about your request. Provide a summary of the request.

We'll add a new option capture_all_matches for the grok processor in OpenSearch, need to document the usage.

Version: List the OpenSearch version to which this issue applies, e.g. 2.14, 2.12--2.14, or all.

3.3.0

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.
opensearch-project/OpenSearch#18799

[gaobinlong]

Please assign this issue to me, I'll open a document PR after the code PR is merged.

[opensearch-ci-bot]

Hi @gaobinlong
,

As part of the entrance criteria, all the documentation pull requests need to be drafted and in technical review.

Since there is no pull request linked to this issue, please take one of the following actions:

• Create the pull request and link it to this issue.
  
• If you already have a pull request created, please link it to this issue.
  
• If this feature is not targeted for the currently labeled release version, please update the issue with the correct release version.
  

Please note: Missing documentation can block the release and cause delays in the overall process.

Thank you!

[gaobinlong]

The original code PR hasn't been reviewed yet, target for next release, please help to remove the label v3.2.0, thanks! @natebower