✨ Support bare IPv6 vCenter server addresses

[tylerschultz]

What this PR does / why we need it:

This PR makes it possible to set VsphereCluster.Spec.Server as an unbracketed IPv6 address. This makes Server consistent with VsphereCluster.Spec.ControlPlaneEndpoint's handling of IPv6 addresses.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #1997

Special notes for your reviewer:

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

Release note:

Support unbracketed IPv6 addresses for `VsphereCluster.Spec.Server`

[k8s-ci-robot]

Hi @tylerschultz. Thanks for your PR.

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[randomvariable]

/ok-to-test

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/retest

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/approve

[k8s-ci-robot]

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/lgtm

[sbueringer]

/cherry-pick release-1.7

[sbueringer]

/cherry-pick release-1.6

[sbueringer]

/cherry-pick release-1.5

[k8s-infra-cherrypick-robot]

@sbueringer: new pull request created: #2011

In response to this:

/cherry-pick release-1.6

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[k8s-infra-cherrypick-robot]

@sbueringer: new pull request created: #2012

In response to this:

/cherry-pick release-1.5

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[k8s-infra-cherrypick-robot]

@sbueringer: new pull request created: #2010

In response to this:

/cherry-pick release-1.7

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[tylerschultz]

Thanks Friends! Much appreciated!