Use DriveInfo constructor to get drive from path

[HebaruSan]

Problem

Discord user HB Stratos reports that sometimes, a 20+ second delay occurs at the start of mod installation:

Cause

Based on the log file provided, the delay happens between here:

CKAN/GUI/Main/MainInstall.cs

Line 204 in 1b5948f

using (TransactionScope transaction = CkanTransaction.CreateTransactionScope())

and here:

CKAN/Core/CKANPathUtils.cs

Lines 135 to 139 in 1b5948f

	log.DebugFormat("Storing {0} to {1} ({2} free)...",
	CkanModule.FmtSize(bytesToStore),
	where.FullName,
	bytesFree.HasValue ? CkanModule.FmtSize(bytesFree.Value)
	: "unknown bytes");

CKAN doesn't do any significant work itself in that interval, but I suspect that there is a hibernating external HDD attached to this user's system, and .GetDrive()'s loop over all the drives causes that drive to be woken up, which takes several seconds. When it's finally ready, the loop continues. That loop was implemented in #3631 because there was no property or function to get the drive associated with a path. However, reading up on the documentation a bit more, DriveInfo's constructor can apparently accept an arbitrary fully qualified path, and returns the associated drive, just as we wanted:

• https://learn.microsoft.com/en-us/dotnet/api/system.io.driveinfo.-ctor
  

In testing, this even seems to work on Linux!

Changes

• The logic from Check free space before downloading #3631 is replaced by calling new DriveInfo(dir.FullName)
• Disk space checking is restored to Linux clients (rolling back Stop trying to check free space on Mono #3850)
• CKANPathUtils.CheckFreeSpace now no longer does anything when its bytesToStore parameter is 0, which will skip some unnecessary IO when installing older modules that don't have install_size defined

This should avoid waking up slumbering HDDs during mod installaiton.