Please add support for mounting FUSE filesystems

[joshtriplett]

(Some of this may not be in scope for this repository; if so, please point to the appropriate place to report the rest.)

The kernel version that Lambda uses has support for mounting FUSE filesystems in a user namespace, if FUSE is enabled. (This was added in Linux 4.18.) This would enable many, many use cases, including using AWS's mountpoint software for S3, and other useful types of shared filesystems.

Enabling this would require:

• The ability to run a user namespace (Allow user namespaces on provided. linux runtimes #143)
• Enabling FUSE in the kernel used on Lambda
• Providing the /dev/fuse character device
• Optionally, providing some of the basic FUSE utilities, though users could also provide those themselves as part of their bootstrap zip.