feat: Support for vSAN Stretched Clusters

[spacegospod]

Summary of Pull Request

Adding a new capability to the cluster resource that enables vSAN to be configured in stretched mode.

The new capability is controlled via a new input property called "stretch_configuration". Inside one can configure both the witness host and the additional hosts that will be commissioned into the cluster.

Removing the new property from a cluster's configuration signals that the cluster should go back into single-site mode (unstretched)

It is not possible to create a stretched cluster via the SDDC manager and this operation is explicitly forbidden in the provider. Users will be advised to first create their cluster and apply the advanced vSAN configuration in a subsequent update.

Type of Pull Request

• [ ] This is a bug fix.
• [X] This is an enhancement or feature.
• [ ] This is a code style/formatting update.
• [ ] This is a documentation update.
• [ ] This is a refactoring update.
• [ ] This is a chore update
• [ ] This is something else. Please describe:

Related to Existing Issues

Issue Number: N/A

Test and Documentation Coverage

For bug fixes or features:

• [X] Tests have been completed.
• [X] Documentation has been added/updated.

Breaking Changes?

• [ ] Yes, there are breaking changes.
• [X] No, there are no breaking changes.

[spacegospod]

@dimitarproynov I renamed "stretch_configuration" to "vsan_stretch_configuration" Which means I have to ask you to stamp this PR one more time

[github-actions[bot]]

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