ES index mode & codec in metricbeat (#49237)

* Add `mode` and `codec` fields to the `elasticsearch.index` metricset in Metricbeat. Update index settings retrieval and mapping to include these new fields.

* Add new exported fields for Elasticsearch in Metricbeat documentation

* Make update

* Added fragment

(cherry picked from commit 7dc72ea)

# Conflicts:
#	docs/reference/metricbeat/exported-fields-elasticsearch.md
#	docs/reference/metricbeat/metricbeat-metricset-elasticsearch-index.md

Author: 3kt

CHANGELOG.asciidoc

@@ -46,6 +46,7 @@ https://github.com/elastic/beats/compare/v8.19.11\...v8.19.12[View commits]
 
 **Metricbeat**
 
+* Added `mode` and `codec` fields to the `elasticsearch.index` metricset.
 * Enforce configurable size limits on incoming requests for `remote_write` metricset (`max_compressed_body_bytes`, `max_decoded_body_bytes`). https://github.com/elastic/beats/pull/48218[#48218]
 
 **Osquerybeat**

changelog/fragments/1772635870-es-index-mode-&-codec-in-metricbeat.yaml

@@ -0,0 +1,45 @@
+# REQUIRED
+# Kind can be one of:
+# - breaking-change: a change to previously-documented behavior
+# - deprecation: functionality that is being removed in a later release
+# - bug-fix: fixes a problem in a previous version
+# - enhancement: extends functionality but does not break or fix existing behavior
+# - feature: new functionality
+# - known-issue: problems that we are aware of in a given version
+# - security: impacts on the security of a product or a user’s deployment.
+# - upgrade: important information for someone upgrading from a prior version
+# - other: does not fit into any of the other categories
+kind: feature
+
+# REQUIRED for all kinds
+# Change summary; a 80ish characters long description of the change.
+summary: Addition of Elasticsearch index mode and codec settings in Metricbeat index stats module.
+
+# REQUIRED for breaking-change, deprecation, known-issue
+# Long description; in case the summary is not enough to describe the change
+# this field accommodate a description without length limits.
+# description:
+
+# REQUIRED for breaking-change, deprecation, known-issue
+# impact:
+
+# REQUIRED for breaking-change, deprecation, known-issue
+# action:
+
+# REQUIRED for all kinds
+# Affected component; usually one of "elastic-agent", "fleet-server", "filebeat", "metricbeat", "auditbeat", "all", etc.
+component: metricbeat
+
+# AUTOMATED
+# OPTIONAL to manually add other PR URLs
+# PR URL: A link the PR that added the changeset.
+# If not present is automatically filled by the tooling finding the PR where this changelog fragment has been added.
+# NOTE: the tooling supports backports, so it's able to fill the original PR number instead of the backport PR number.
+# Please provide it if you are adding a fragment for a different PR.
+# pr: https://github.com/owner/repo/1234
+
+# AUTOMATED
+# OPTIONAL to manually add other issue URLs
+# Issue URL; optional; the GitHub issue related to this changeset (either closes or is part of).
+# If not present is automatically filled by the tooling with the issue linked to the PR number.
+# issue: https://github.com/owner/repo/1234