Teach vcpkg fetch to handle msi files

[ras0219-msft]

This PR adds .msi support to vcpkg fetch in order to enable upgrading 7zip to a more recent version (19.00). We must use the MSI package because it is one of the few formats that can be supported on a completely stock Windows machine.

Once this change is applied, we'll replace the 7zip entry in vcpkgTools.xml with:

    <tool name="7zip" os="windows">
        <version>19.00</version>
        <exeRelativePath>Files\7-Zip\7z.exe</exeRelativePath>
        <url>https://www.7-zip.org/a/7z1900-x64.msi</url>
        <sha512>7837a8677a01eed9c3309923f7084bc864063ba214ee169882c5b04a7a8b198ed052c15e981860d9d7952c98f459a4fab87a72fd78e7d0303004dcb86f4324c8</sha512>
        <archiveName>7z1900-x64.msi</archiveName>
    </tool>

As a side benefit, this allows us to use 7zip to unpack .nupkg files in the future, since we will no longer require nuget to unpack 7zip.

[BillyONeal]

What happens if 7z is already installed?
Does this make it show up in add/remove programs?

[ras0219-msft]

No, /a is the "Administrative install mode" (poorly named) which extracts the package contents without modifying the current system.

From https://docs.microsoft.com/en-us/windows/win32/msi/administrative-installation:

The Windows Installer can perform an administrative installation of an application or product to a network for use by a workgroup. An administrative installation installs a source image of the application onto the network that is similar to a source image on a CD-ROM. Users in a workgroup who have access to this administrative image can then install the product from this source. A user must first install the product from the network to run the application. The user can choose to run-from-source when he installs and the installer uses most of the product's file directly from the network.

Which is clear as mud, but basically my understanding is that you could use the administrative install to eventually perform a full machine install later.

[BillyONeal]

No, /a is the "Administrative install mode" (poorly named) which extracts the package contents without modifying the current system.

From https://docs.microsoft.com/en-us/windows/win32/msi/administrative-installation:

The Windows Installer can perform an administrative installation of an application or product to a network for use by a workgroup. An administrative installation installs a source image of the application onto the network that is similar to a source image on a CD-ROM. Users in a workgroup who have access to this administrative image can then install the product from this source. A user must first install the product from the network to run the application. The user can choose to run-from-source when he installs and the installer uses most of the product's file directly from the network.

Which is clear as mud, but basically my understanding is that you could use the administrative install to eventually perform a full machine install later.

OK, I'm convinced. Approve-with-suggestion to add that test