[virtcon] Make run-vc agnostic to fdio implementation

Bug: US-534 #done
Bug: ZX-2680 #done
Test: Check that run-vc works
Change-Id: Icb733697aa5b1f10acca57503e40d6d969dd12c4

[run-vc] Switch to fdio_spawn_etc

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

Test: Manually verified that run-vc continues to work.

Change-Id: Ia14c077bb7f4a88c409f47208d2c6427b79e9bee

[fdio] Move headers into lib/fdio/...

Change-Id: Ie8d74e716da913bf6e2672c4acf8cd67b4962b7f

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[launchpad] Add LP_CLONE_MXIO_NAMESPACE

This constant has the same value and semantics as LP_CLONE_MXIO_ROOT but refers
to namespaces, which will shortly replace MXIO_ROOT.

Change-Id: Ida671c001b45046cf36b39754f24f04aad3160a5

[gfxconsole][run-vc][dmctl] support run-vc in new virtcon service

Change-Id: I3ea3502e2d55dc9cefbde8561993803a6ead8d46

[dash][run-vc] Remote ApplicationEnvironment code

Now that we use namespaces in Fuchsia-land, we don't need the
ApplicationEnvironment-related code anymore.

Change-Id: Iae4181bd72efa63b59d97c46c61994644aac7193

[processargs] tidy up naming and numbering

This cleans stuff up ahead of the addition of string tables for
the upcoming PA_NS_DIR and PA_NS_REQ types and the eventual
flattening of PA_MXIO_* to a single type, using subtypes for
protocol.

- Align names with current-day usage
- Organize numbering / ordering around subsystem usage
- Reduce "type" field to 8 bits
- Reserve space for "subtype" field
- Use PA_ namespace and shorter a lot of very long names

Change-Id: I5e59f412c3b9bd79d90f921a248a6d98d4b703bc

[mxio] add event to mxio_watch_directory() callback

- WATCH_EVENT_ADD_FILE is the existing implied event
(a new file was added to the watched directory)

- WATCH_EVENT_WAITING is a new event which informs
the watcher callback that the watcher has started
waiting for new files to be added (meaning it has
already been informed of all the files that existed
when mxio_watch_directory() was called)

Updated all call sites.

Change-Id: I3354d011ad65f055626b1375ae03986d2b7fa231

[run-vc] Watch for virtual consoles to exist

Previously, if you tried to use run-vc during startup, the virtual
console device might not have been created yet. This patch teaches
run-vc to watch the directory in which the virtual console will appear
so that it can create the virtual console at the correct time.

Change-Id: I146ca0c241c9500131447dcf97b332d2dd7a1cc9

[run-vc] Forward the application environment handle

Forwarding the application environment handle means we can use this program
from Fuchsia to spawn virtual consoles easily.

Change-Id: Id58d66aa0551d3a33adbd9f81bdd02292a57cff6

[launchpad] stop using deprecated apis

Change-Id: Ie627c281523f61792ece8fe49234782ae7580c84

[devmgr][mxio] Add a system-wide loader service

Add a dmctl ioctl to get a handle to a shared system loader service,
which translates paths like "libhid.so" into VMOs containing the named
object's data.

Launchpad and other users of mxio_loader_service() will automatically
prefer the system loader service if available.

Before this, loading was done by in-process threads, which meant that
those processes needed filesystem access. This is a step towards
supporting dynamic binaries with no filesystem rights.

For now, the system loader service uses the same code as the in-process
loader service, but this may change. It also needs to be smarter to
avoid starvation from bad processes (MG-491).

Moving the loader-related prototypes to a new header caused some ripple
effects for code that depended on transitive includes from mxio/util.h.

For MG-451: "loader service"

Change-Id: I8adb534b55f96334017e979da6af263e19095d84

[jobs] Jobify run-vc

Change-Id: Id19a34ee610f6c7bd4b10d1b3b19baff2c52cda2

[netsvc][run-vc] Use dash instead of mxsh

Change-Id: Id78285c56a741a1ce6f3b3c981c379fb4d7183d6

[system] wire the jobs to launchpad and devmgr

This change wires 'most' but not all of the
users of launchpad.

It is a transitional change, so the system uses jobs
while not having to change all callers

There are 3 strategies for the job:

1- pass 0, that works today
2- let launchpad get it from mxio_get_startup_handle()
3- provide own job

For option 3, there are two options

a- create a child job from the mxio_get_startup_handle()
b- duplicate mxio_get_startup_handle()

All of those are in this CL.

Change-Id: I7e141a0ab9fc841191f9ba909804267c9bb774e0

[system] align license and license banners with Fuchsia

This adjusts the Magenta userspace code to match the prevailing
license in Fuchsia (three-clause BSD), using the same banner
and license text.

Change-Id: I6b6d79435c5dbaa32027888874849e4f47aaa7be

[uapp] [run-vc] Use launchpad in run-vc

The old mxio process-launching code is going away.
Don't use it any more.

Change-Id: I4e8974696c13fc5545018d697d197775c1b0625b

[uapp] add an app to run a process in a new vc

Change-Id: Ieacf0185b72dc0e9e177974937700e0597150ee4