[8.15](backport #40634) [vSphere][datastore_cluster] Add support for new metrics in datastore_cluster metricset

[mergify]

Description

Here are the following metrics to be added for the datastore cluster data stream in the vSphere metricbeat module. Here we added a new performance API to get more detailed information from vSphere.

Metrics Type	Metrics	API	Field Mappings
Datastore cluster capacity	StoragePod.Summary.Capacity	Summary	capacity.bytes
	StoragePod.Summary.FreeSpace	Summary	free_space.bytes

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Related issues

• Relates https://github.com/elastic/obs-integration-team/issues/30

---

This is an automatic backport of pull request #40634 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 30320a3 has failed:

On branch mergify/bp/8.15/pr-40634
Your branch is up to date with 'origin/8.15'.

You are currently cherry-picking commit 30320a3bfc.
  (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/fields.asciidoc
	new file:   metricbeat/docs/modules/vsphere/datastorecluster.asciidoc
	modified:   metricbeat/include/list_common.go
	new file:   metricbeat/module/vsphere/datastorecluster/_meta/data.json
	new file:   metricbeat/module/vsphere/datastorecluster/_meta/docs.asciidoc
	new file:   metricbeat/module/vsphere/datastorecluster/_meta/fields.yml
	new file:   metricbeat/module/vsphere/datastorecluster/data.go
	new file:   metricbeat/module/vsphere/datastorecluster/data_test.go
	new file:   metricbeat/module/vsphere/datastorecluster/datastorecluster.go
	new file:   metricbeat/module/vsphere/datastorecluster/datastorecluster_test.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   metricbeat/docs/modules/vsphere.asciidoc
	both modified:   metricbeat/docs/modules_list.asciidoc
	both modified:   metricbeat/metricbeat.reference.yml
	both modified:   metricbeat/module/vsphere/_meta/README.md
	both modified:   metricbeat/module/vsphere/_meta/config.reference.yml
	both modified:   metricbeat/module/vsphere/_meta/config.yml
	both modified:   metricbeat/module/vsphere/_meta/docs.asciidoc
	both modified:   metricbeat/module/vsphere/fields.go
	both modified:   metricbeat/modules.d/vsphere.yml.disabled
	both modified:   x-pack/metricbeat/metricbeat.reference.yml

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

[botelastic]

This pull request doesn't have a Team:<team> label.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b mergify/bp/8.15/pr-40634 upstream/mergify/bp/8.15/pr-40634
git merge upstream/8.15
git push upstream mergify/bp/8.15/pr-40634

[ishleenk17]

Closing in lieu of #40829