VNet docs: Provide clear instructions for getting debug logs

[ravicious]

We've been dealing with an increased amount of customer tickets regarding VNet. While working through them, I noticed a couple of issues with the docs, specifically the section about submitting a VNet-related issue:

1. The docs describe how to get VNet logs and then they redirect to Teleport Connect docs page for how to get Connect's logs. The user must read and understand sections from those two pages and then form a plan themselves on what to do to submit a good issue.
2. The docs first describe how to get the logs and later they mention how to enable debug logs. In practice, the regular logs don't provide enough value for non-trivial issues.
3. The docs include a lot of information about how logs are stored which is more relevant for Teleport devs than customers.
4. When I originally wrote that section, I didn't realize that it actually is possible to enable debug logs for VNet on macOS.
5. The Windows section talks about setting TELEPORT_DEBUG=1 as a system variable which enables debug mode in any Teleport tool on the system.

This PR addresses each of those points:

1. The section on submitting an issue now includes a step-by-step instructions on how to start Connect and VNet with debug logs. The user can just follow instructions instead of having to understand how Connect and VNet work together.
2. The docs now explicitly instruct the user to provide debug logs.
3. There's much less focus on specific aspects of os_log and Event Viewer. The docs describe how to get logs so that they can be submitted with the issue, rather than general instructions on how to browse the logs.
4. The docs now include info on how to enable debug logs for VNet on macOS.
5. The Windows section now gives the user commands that enable the debug logs only for the VNet service.

[github-actions]

Amplify deployment status

Branch	Commit	Job ID	Status	Preview	Updated (UTC)
r7s/vnet-docs-update	5f6fa65	3	✅SUCCEED	r7s-vnet-docs-update	2025-06-26 10:52:36

[ptgott]

I would work the comment into the preceding paragraph so the user doesn't remove the && exit, e.g.:

debug logs in VNet. The `&& exit` at the end of the command prevents you from starting Connect from the admin command prompt.

[backport-bot-workflows]

@ravicious See the table below for backport results.

Branch	Result
branch/v17	Failed
branch/v18	Create PR