fix(scoop-download): Add failure check

[tech189]

Description

• When scoop-download catches an error in dl_with_cache, now a variable is saved so that the final success message will not appear.
• When aria2 is enabled but not installed, Test-Aria2Enabled now warns the user that the standard download method will be used instead of aria2

Motivation and Context

Closes #4810

How Has This Been Tested?

I tested running this without internet and the failure was successfully caught, I tested both with aria2 and without so I have tested dl_with_cache and dl_with_cache_aria2.

This shows both changes in action:

❯ scoop config aria2-enabled
True

~
❯ c:\Users\me\Documents\GitHub\Scoop\libexec\scoop-download.ps1 protobuf
INFO  Starting download for protobuf...
WARN  aria2 is enabled but not installed, using standard download instead.
No such host is known. (github.com:443)
ERROR URL https://github.com/google/protobuf/releases/download/v3.19.4/protoc-3.19.4-win64.zip is not valid

^^ see no "success" and a warning about aria2!

Checklist:

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

^^ is there any documentation I should add and are there any tests to update?

[rashil2000]

When aria2 is enabled but not installed, Test-Aria2Enabled now warns the user that the standard download method will be used instead of aria2

I don't think we should do this. The default value of aria2-enabled config variable is always true, meaning that the warning will always be shown to users who are new to Scoop, and users who have never installed aria2. This will be annoying for some people, and is a breaking UX change.

[tech189]

Oh, I didn't know that aria2-enabled is set to true by default for new users. Why is it set to true if aria2 is not installed by default?

[rashil2000]

Why is it set to true if aria2 is not installed by default?

See https://github.com/ScoopInstaller/Scoop#multi-connection-downloads-with-aria2

Aria2 was supposed to provide a better (and resumable) download experience, so the devs enabled it by default. The only requirement was installing aria2

[tech189]

Huh weird, kinda defeats the point of having a config if it's on by default but doing nothing. But anyway yeah I'll get rid of that warning/check.

[rashil2000]

LGTM. Please update the changelog (with same entry as the PR's title).

[tech189]

Done! Are there any tests to run?

[rashil2000]

No