[paver][fvm] Implement partition wiping, FVM-resizing, flushing in paver

- Allow the "SkipBlockDevicePartioner" to wipe devices by clearing
the FVM partition.
- Allow paving of FVM images with mismatch slice sizes by overwriting
the underlying FVM.
- Implement "Flushing" in the paver, for block devices which might
have an in-memory cache. Utilize flushing after streaming partitions
and wiping partitions.
- Update the FVM driver to rebind when requested (necessary to
re-initializing FVM with a new slice size).

Test: Manually paving
ZX-2141 #comment In Progress

Change-Id: Iafff65a7ecaf693138061ef631ac429accc6b422

[paver][test] Add unit tests to the paver tool.

Change-Id: Ib61123b3ae8ccc0573928e74a3f9d858757d0014
Tested: runtests -t install-disk-image-test

[disk-pave] Add support for paving bootloader.

Currently only enabled for Astro and Gauss.

Change-Id: I5f64795039bbeaaf359b05ff74fc889e6c19d782
Tested: Paved bootloader to Astro.

[paver] Add support for non-managed NAND partitions.

On several NAND parts, we have NAND partitions managed by a special
skip-block algorithm, rather than an FTL. These do not expose a block
IOCTL interface, but rather a skip-block IOCTL interface; we simply use
that instead.

In addition, ZBI validation was temporarily disabled until we add
support for either skipping validation of signed payloads or add support
for validating signed payloads.

Change-Id: Icb6bbdcb151b1127f95509aee55683db52ab80b6
Tested: Paved ZIRCON-A/ZIRCON-R to a gauss and astro.

[disk-pave] Add support for ARM platforms to paver

A new device-partitioner implementation was added that doesn't expect a
GPT was added. It does not have the ability to remove partitions or add
them, but rather only find them.

In addition, the new paver implementation works with the ZIRCON-A/B/R
partition layout instead of EFI/KERN-C partitions that ChromeOS and EFI
based systems expect.

Tested:
Manually tested paving on pixelbook and vim2.

Change-Id: I49005a8376e00fa034bfc77b7c0ffe752712207b

[disk-pave] Rewrite paver

An additional abstraction layer of a "device partitioner" interface was
added to the paver to allow for non-GPT device implementation to be
added more easily.

Tested:
Manually tested paving on pixelbook and nuc.
Tested wipe command followed by paving.
Tested paving to same device twice in a row.

Change-Id: I6b0d79c4702e20342e60125d15832e7fbb0b39fe