[BUG] registry update broke registry file

[mbl-35]

When following command :

wslctl registry update

and the file already exists in the user %LOCALAPPDATA%/Wslctl/Registry/register.json, its content is not correctly copied from remote.

v-2.0.4

[mbl-35]

We use OpenWrite method in FileUtils.psm1. As said at file-openwrite-appends-instead-of-wiping-contents, the file is not truncated when it exists.

Then :

• create a temporary file to download the remote registry file
• move that temporary file to the local registry file