fix(powershell): handle unavailable Update-Module

[niStee]

What does this PR do

Closes #1443.

This changes the PowerShell module update step to avoid passing -Force to Update-Module when --yes is used. Instead, it passes -Confirm:$false and conditionally adds AcceptLicense when the installed Update-Module supports it.

It also checks whether PowerShellGet can provide Update-Module before running the update. If Update-Module is unavailable or cannot be loaded, Topgrade now prints a warning and marks the step as skipped instead of failing with a command-not-found error or reporting OK after doing no update.

This helps Windows PowerShell 5.1 setups where PowerShellGet/PackageManagement are broken, blocked by cloud-backed module folders, or otherwise cannot be autoloaded.

Standards checklist

• The PR title is descriptive
• I have read CONTRIBUTING.md
• Optional: I have tested the code myself, with the relevant tools installed. If yes, add Topgrade's output of the relevant steps.
• If this PR introduces new user-facing messages they are translated

AI involvement

I used AI assistance while investigating the PowerShell behavior, drafting the code change, and running local checks. I reviewed the changes myself before submitting.

[niStee]

Tested with:

• cargo fmt --check
• cargo test
• cargo clippy --all-targets -- -D warnings
• Manual PowerShell checks with PowerShell 7, Windows PowerShell 5.1, gsudo, and native Windows sudo.