Zowe Explorer validation shouldn't hang for an unreachable endpoint

[zFernand0]

Describe the bug

Zowe Explorer hangs when there is an invalid host property specified.

To Reproduce

See:

• Incorrect profile specification can cause profile validation to hang #3364

Expected behavior

Zowe Explorer should inform about the problematic host property

Additional context

Spin-off from #3364

[github-actions]

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[awharn]

This issue will likely require a timeout during validation in the REST client. This is triggered by the server being resolved by DNS, but a firewall dropping inbound traffic, causing the server to not respond.