[7.x](backport #28287) Add the cluster_uuid field to Enterprise search stats metricset

[mergify]

This is an automatic backport of pull request #28287 done by Mergify.
Cherry-pick of 78bcab3 has failed:

On branch mergify/bp/7.x/pr-28287
Your branch is up to date with 'origin/7.x'.

You are currently cherry-picking commit 78bcab36c7.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   metricbeat/docs/modules/enterprisesearch.asciidoc
	modified:   metricbeat/docs/modules/enterprisesearch/health.asciidoc
	modified:   metricbeat/docs/modules/enterprisesearch/stats.asciidoc
	modified:   metricbeat/docs/modules_list.asciidoc
	modified:   x-pack/metricbeat/metricbeat.reference.yml
	modified:   x-pack/metricbeat/module/enterprisesearch/_meta/fields.yml
	modified:   x-pack/metricbeat/module/enterprisesearch/fields.go
	modified:   x-pack/metricbeat/module/enterprisesearch/health/_meta/docs.asciidoc
	modified:   x-pack/metricbeat/module/enterprisesearch/health/_meta/fields.yml
	modified:   x-pack/metricbeat/module/enterprisesearch/health/_meta/testdata/health.json-expected.json
	modified:   x-pack/metricbeat/module/enterprisesearch/health/data.go
	modified:   x-pack/metricbeat/module/enterprisesearch/health/health.go
	modified:   x-pack/metricbeat/module/enterprisesearch/stats/_meta/docs.asciidoc
	modified:   x-pack/metricbeat/module/enterprisesearch/stats/_meta/fields.yml
	modified:   x-pack/metricbeat/module/enterprisesearch/stats/_meta/testdata/stats.json
	modified:   x-pack/metricbeat/module/enterprisesearch/stats/_meta/testdata/stats.json-expected.json
	modified:   x-pack/metricbeat/module/enterprisesearch/stats/data.go
	modified:   x-pack/metricbeat/module/enterprisesearch/stats/stats.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   metricbeat/docs/fields.asciidoc

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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• Start Time: 2021-10-18T15:59:04.648+0000

• Duration: 112 min 36 sec

• Commit: 321f5f3

Test stats 🧪

Test	Results
Failed	0
Passed	9622
Skipped	2449
Total	12071

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