(#3613) Add source uri override for download uris

[AdmiringWorm]

Description Of Changes

This adds a new Package Downloader class and have it call a resolve
redirection for download URIs to the original source URI.

This allows the same credentials to be used for the download URI as with
the source URI when the server is configured to store binary files in
a different location.

Motivation and Context

Without this change, it makes it impossible to install packages that have a download location that do not have the source URI as its prefix.

Testing

1. Install a package from the following location. CCR, Licensed Feed, Nexus Feed and ProGet feed, local package directory and a remote package directory.
2. Install another package, that have one or more dependencies with the above feed types.

Operating Systems Testing

• Windows 10

Change Types Made

• Bug fix (non-breaking change).
• Feature / Enhancement (non-breaking change).
• Breaking change (fix or feature that could cause existing functionality to change).
• Documentation changes.
• PowerShell code changes.

Change Checklist

• Requires a change to the documentation.
• Documentation has been updated.
• Tests to cover my changes, have been added.
• All new and existing tests passed? (A few failures locally, but these have been seen before and only on my VM)
• PowerShell code changes: PowerShell v3 compatibility checked?

Related Issue

• Fixes Unable to upgrade packages on certain authenticated feeds #3613

[corbob]

Just one minor style thing. And a gripe about BOM and diff interfaces: I have no way of telling without a bunch of manual work if the files that got new copyright lines also changed their BOM/encoding like the csproj file 😬

[corbob]

The ubuntu GHA is failing because mono isn't on that version anymore. Would we want to bring a maint commit that mirrors this one: ecd3e4e

[AdmiringWorm]

The ubuntu GHA is failing because mono isn't on that version anymore. Would we want to bring a maint commit that mirrors this one: ecd3e4e

I plan to, but it won't be until after this PR (most likely).

However, feel free to cherry-pick it into the hotfix branch if you want.

[corbob]

Looks good to me. All of the tests I put at it worked as expected.

[corbob]

Thanks for getting this updated @AdmiringWorm 👍