Fully support user-scoped install scripts on Windows

Goal

User story
As a Fleet admin,
I want to install a Windows user-scoped program reliably
without waiting for the user to be logged in.

Context

Some Windows programs can only be installed in user-scope, such as Figma.

As covered in #20000, the downside of our example user-scoped install script is that the end user must be logged in. That means if the user turns on their laptop, but doesn't log in for a few minutes, Fleet may attempt a user-scoped install/uninstall and will fail. We can attempt to solve this issue by having Fleet or fleetd check if the user is logged in before running the script.

Another issue with the user-scoped script is that it lacks debug information since the script runs as a separate process. We should gather the logs from the user process and report them back to Fleet.

Requestor(s): _____
Product designer: _____

Changes

Product

[ ] Reference documentation changes: TODO
[ ] UI changes: TODO
[ ] CLI (fleetctl) usage changes: TODO
[ ] YAML changes: TODO
[ ] REST API changes: TODO
[ ] Fleet's agent (fleetd) changes: TODO
[ ] Activity changes: TODO
[ ] Permissions changes: TODO
[ ] Changes to paid features or tiers: TODO
[ ] Once shipped, requester has been notified

Engineering

[ ] Feature guide changes: TODO
[ ] Database schema migrations: TODO
[ ] Load testing: TODO

ℹ️ Please read this issue carefully and understand it. Pay special attention to UI wireframes, especially "dev notes".

QA

Risk assessment

Requires load testing: TODO
Risk level: Low / High TODO
Risk description: TODO

Manual testing steps

Step 1
Step 2
Step 3

Testing notes

Confirmation

[ ] Engineer (@____): Added comment to user story confirming successful completion of QA.
[ ] QA (@____): Added comment to user story confirming successful completion of QA.

fleetdm / fleet