fix(core): Ensure manipulating config with UTF8 encoding

[chawyehsu]

Description

Use utf8 encoding in scoop's and aria2's config

Motivation and Context

Fixes #4629

How Has This Been Tested?

New unit tests introduced.

Checklist:

• I have read the Contributing Guide.
• I have updated the documentation accordingly.
• I have updated the tests accordingly.

[niheaven]

Maybe New-Item is another choice.

I found in its docs that: (-ItemType File)

When you create a file using this method, the resulting file is encoded as UTF-8 without a byte-order-mark (BOM).

[chawyehsu]

I've updated the implementation by referring the simpler Puppet.Dsc's implementation and updated the tests. The tests failed under WindowsPowerShell on CI, which can't be reproduced on my local environment.

@niheaven Need your help. You may look at and review the new commits and see if it can be bundled into the upcoming release.

[niheaven]

I'll check it tomorrow.

[niheaven]

@chawyehsu It is a bug of Pester/PS5 when test file contains non-ASCII characters. Using [Regex]::Unescape to avoid it.

Although change [System.IO.File]::ReadAllText to [System.IO.File]::ReadAllLines to keep consistence.

[chawyehsu]

LGTM