[fs][fidl] Replaced filesystem ioctls with FIDL.

This patch allows "ioctl" to be removed from the
C++ VFS Vnode interface.

IOCTL_VFS_MOUNT_FS -> Mount()
IOCTL_VFS_UNMOUNT_FS -> Unmount()
IOCTL_VFS_UNMOUNT_NODE -> UnmounteNode()
IOCTL_VFS_QUERY_FS -> QueryFilesystem()
IOCTL_VFS_MOUNT_MKDIR_FS -> MountAndCreate()
IOCTL_VFS_GET_DEVICE_PATH -> GetDevicePath()
IOCTL_VFS_WATCH_DIR -> WatchDir()

Test: fs-management / fs / blobfs / fvm tests, df manually

Change-Id: Iefe8ec251ca6b8f4e4578ceb61bae6dff7a59e3d

[memfs] Split memfs into C / C++ libraries

For clients which utilize memfs to create
temporary filesystems, export a C ABI shared
library.

Internally, this C library uses a C++ library,
which is exported as source.

Change-Id: I73b95a2a2b8c4870d1b07f5f2f2525f4b0cd4e9f

[minfs] [blobfs] Update behavior when FVM slice counts differ.

When FVM reports a lower slice count than Blobfs or Minfs,
automatically fail, since it is possible that one or more of the
slices expected by the file system has data allocated to it.

When FVM reports a higher slice count, always attempt to shrink
the FVM - assume that the file system is the source of truth.
Since those slices aren't expected to be there, we aren't losing
any crucial data by shrinking them.

Change-Id: I44e7cde936b8df435564c86f432a474141ac0e6b

[fvm] Execute fvm tests on mount point in local namespace

This patch reduces the dependency on global "/tmp".

ZX-1939 #comment Done

Change-Id: I2f6103398b73705dc6e3b97e42fc400dc63496cd

[fvm] Use block offsets defined by Minfs format

Change-Id: I19c5347fb072b6db478358f58252c2ba7024a572

[digest] Switch from cryptolib to uboringssl

This CL switches the SHA-256 implementation for ulib/digest to use
uboringssl, which includes optimized assembly and hardware acceleration
to provide better message digest performance.

Change-Id: Id3dedbc8232b4f4491b19fe46ef9e1415eea7358

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[zircon][mxtl->fbl] Rename mxtl to fbl

Change-Id: Ie21b6498e1bfb0a7fa0315e40b9e5c3ee78646be

[fvm] Fix FVM bug for multi-slice iotxns

Additionally, upgrade tests to check for this condition
more aggressively. Previously, although the FVM driver had
code to test "read / writes crossing multiple noncontiguous slices",
the client wrapper code for read/write only transmitted messages
in units of 8KB. As a consequence, the "multi-slice txns"
actually were broken down into many "single-slice txns".

To remedy this issue, I have integrated helper classes
into the FVM tests which wrap the "Fast Block I/O" protocol,
and actually permit these large transactions. Updated
the "NonContiguousPhysical" test to check for this behavior.

Change-Id: I917929f36b22698b0d3c755e0a53657e600db10b

[fvm] Initial commit of Fuchsia VPartition Manager

Change-Id: I1dd488889dd440814277629ffbcfd6d57cf30f47