[vSphere][datastore_cluster] Add support for new metrics in datastore_cluster metricset

[kush-elastic]

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

[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 30-implement-the-datastore_cluster-metricset-beats-changes upstream/30-implement-the-datastore_cluster-metricset-beats-changes
git merge upstream/main
git push upstream 30-implement-the-datastore_cluster-metricset-beats-changes

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @kush-elastic? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v8./d.0 is the label to automatically backport to the 8./d branch. /d is the digit

[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 30-implement-the-datastore_cluster-metricset-beats-changes upstream/30-implement-the-datastore_cluster-metricset-beats-changes
git merge upstream/main
git push upstream 30-implement-the-datastore_cluster-metricset-beats-changes

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[devamanv]

Shared a few more review comments. Rest looks good.

[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 30-implement-the-datastore_cluster-metricset-beats-changes upstream/30-implement-the-datastore_cluster-metricset-beats-changes
git merge upstream/main
git push upstream 30-implement-the-datastore_cluster-metricset-beats-changes