When using a query parameter without a scheme, the scheme defaults to
`file`. This results in the files in the explorer being technically
different from the file picker files because they are file:// instead of
vscode-remote://, causing the same file to open twice and causing
numerous issues.
Normally the file explorer wouldn't even load at all in this case but we
provide a file service for file:// URLs as a failsafe for certain files
that wouldn't load correctly in the past. These files load fine now
using the vscode-remote scheme, so I'm also removing that service.
Related: #1351.
Fixes#1294.
d574012871