[netboot][zbi] Support complete ZBI booting

When netboot receives only a "kernel.bin" and no "ramdisk.bin",
it expects the single file to be a complete ZBI. It splits the
kernel from the data ZBI and passes both to mexec.

The BOOTLOADER_VERSION is bumped to 0.7.9 for this change, to
indicate a netboot that's capable of booting a complete ZBI.
This means that with this change, new and old zedboot images and
host-side bootserver tools will be incompatible. (That is,
bootserver will refuse to serve a differently-versioned zedboot
even though in this case it would work as long as either the old
method with separate ramdisk image was being used, or the zedboot
was a new one.)

Test: CQ + manual netboot with both old and new methods
Change-Id: I63ff688e491e5f956ffc46f7284f613bad2d3633

[netsvc] Switch to fdio_spawn_etc

Most codepaths that create processes should use fdio_spawn rather than
launchpad directly.

Test: Manually verified that netruncmd and paving continue to work.
Change-Id: Ib5a6596921c2bd8f65e80c47bc995960bd35b378

[netsvc] Revert "Switch to fdio_spawn_etc"

This reverts commit 8a28ca4959dea54349d1c7aacfb76d83492d4b1e.

The original change breaks the paving flow.

TEST=manual

Change-Id: Id37551f30a6183adfebae3dc6d67fadac2555bff

[netsvc] Switch to fdio_spawn_etc

Most codepaths that create processes should use fdio_spawn rather than
launchpad directly.

Test: Manually verified that netruncmd and paving continue to work.
Change-Id: If9c079e7f620f41b74845782f1944aaa5ad0a142

[netsvc] Add intermediate buffer to paver

When paving, store incoming tftp data to a buffer so that the ethernet
receive buffers don't fill up. This introduces an additional thread of
execution - one to receive the eth data and one to write it out to the
paver process.

ZX-1521

Change-Id: Ic2a05c195a872deed8975727ee85526072d932f9

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[build][groups] annotate 'misc' and 'test' modules

This allows us to generate a bootdata.bin which excludes them,
reducing it from 4.52MB to 2.65MB

The default bootdata.bin still includes all modules.

Change-Id: If13bfcacba9386a691e6b7c380eed53d67bb44eb

[netsvc] Refactor debuglog support

Move debuglog support into a separate compilation unit. This should
simplify things quite a bit when adding another timeout source (tftp).

Also, give a name to the debuglog magic number (NB_DEBUGLOG_MAGIC).

Change-Id: Id47f6503cb74cbfb535326d60993daf4b128befd

[netsvc] Add tftp support

Adds support for handling incoming tftp requests, which are received on
NB_TFTP_INCOMING_PORT and then processed using NB_TFTP_OUTGOING_PORT.

Change-Id: I13cf77b6addcc6a302127fb00c78466f96928a86

[netsvc][netboot] Implements netboot in magenta

Change-Id: Ic85235dbabf1dbcf4fad136ee723c5d15eaac59d

[build] flatten the build

Previously we treated kernel/, system/, and third_party/ as
overlays on a shared namespace. This required the concept
of "canonical" module names, and a lot of complexity to ensure
that things didn't collide and the build worked.

This change gets rid of that, no longer passes -I to make,
so that include directives from our *.mk files do not magically
wildcard across various paths, etc.

The most user-visible change is that everywhere where a module
name is specified (MODULE_DEPS, MODULE_LIBS, etc), full module
names like kernel/lib/io or system/ulib/mxio must be used instead
of previously-allowed "short" names like lib/io and ulib/mxio.

The build output still has a similar shape, but the first segment
of the module path (kernel/, system/, or third_party/) is no
longer elided under $(BUILDDIR)

Change-Id: I525aba1da1c86eb7a86007bddc669f7eeebfedd5

[build][musl] refer to musl libc as ulib/c

This makes the build rules and the intermediate
output files easier to understand, without having
to modify the path where musl libc lives.

The biggest observeable difference is the build
intermediate files:

$ ls build-magenta-pc-x86-64/ulib/c
config-module.h libc.abi.h libc.abi.stamp libc.so libc.so.id libc.so.strip
libc.a libc.abi.o libc.a.opts libc.so.abi libc.so.opts third_party

which previously were at build-magenta-pc-x86/ulib/musl
and named libmusl.*

and the replacing of ulib/musl with ulib/c in the library
dependencies of all the rules.mk files (the vast bulk of
this change)

Change-Id: If9c5d522099d2c9ac5bdb666b8e67a2eb3d316ee

[netsvc] Generate unique nodename

Use mac address and EFF Diceware short list to generate a unique
nodename for the device.

Change-Id: I70056ada45250662733d986236612a72a489bd1e

Revert "[netsvc] Generate unique nodename"

This reverts commit bd31874b6688ecc2e3feecd103eefe0ca2946de5.

Change-Id: I2748c62b549f559f6d0e5e680e62e3abba64e155

[netsvc] Generate unique nodename

Use mac address and EFF Diceware short list to generate a unique
nodename for the device.

Change-Id: I0cad02524e9879b9bbcd88b028e511d9fe2e8aff

[ethernet][libeth] switch to new magenta fifos

- add a bunch of documentation to device/ethernet.h
- libeth is no more: the new protocol requires much less boilerplate
- eth-client.c is absorbed into inet6

Change-Id: I0e66d0f449489d8d57efb7db853d447d60eec41a

[inet6] Allow netsvc to use ethernet fifos

netsvc will attempt to get a fifo from an ethernet device. If it
succeeds, it will use that fifo for rx/tx with the device. Otherwise
it will fall back to using read/write.

Change-Id: I9099bd69f8a18169e775480a4b9753cc236fe86e

[organization] move essential userspace components to system/core/...

userboot, devmgr, acpisvc, crashlogger, netsvc are essential to the
system booting and running. Pretty much everything else in system/uapp/..
is nonessential.

Change-Id: Ibbcf2b1c388bdefc28699226eab02e90aab895f0