[fdio] Remove unused functions from private-remoteio.h

Many of these functions are now only called from remoteio.c and
therefore do not need to be declared in a header.

Test: No behavior change
Change-Id: I2162243b075a73c4e6a66bba193ba0cedec9576f

[fdio] Remove h2 to event

This handle is now always an "event" handle. We can use a more specific
name.

Test: No behavior change
Change-Id: I27d1b10d06172f591dada81ac00a2b1a2919d61b

[fd] Rename zxrio_object_info_t to zxrio_node_info_t

The new name matches the name in the FIDL protocol.

Test: No behavior change.
Change-Id: I742b72c2adbbaaf6aa16063edad7126a31d74bae

[fdio] extend fdio_get_service_handle() to work with all fidl fds

Previously this only worked on opaque "service" fds. Now you can
use it to extract the underlying channel handle from a file/dir/device
fd as well.

Also fixed it to correctly downref and destroy the fdio_t, improved
error handling and docs.

Test: boot & runtests
Change-Id: I45988ce1eead8a20c10f9dc882406e2e043b4c01

[fdio][channel-call] remove client-side txid management

The kernel now handles this for us.

Change-Id: I02a87b1d8017890f4d6fa6287ae4053ae81650c5

[fidl] Rename fidl2 things to just fidl

Change-Id: I17780c327272c554b4c80a7c5fc64df78d0a5601

[rio][fidl] Convert RemoteIO operations to FIDL2

This patch updates all Zircon servers to respond to
either RIO or FIDL2 requests. This will allow
compatibility with clients speaking either protocol.

Although this patch allows clients and servers to communicate
with FIDL2 instead of RIO, it is a slight modification
from strict FIDL2 standards: Most servers don't implement
the exact FIDL2 Object / Node / File / Directory protocols,
they just implement a subset of all operations. Updating
these servers to exactly implement these interfaces
will occur in subsequent patches.

ZXRIO_FIDL toggle can be used to request RIO or FIDL2 client
requests.

TO-496 #done
ZX-1358 #comment In Progress

Change-Id: Ia52f469e553be977deb3d0f280ba3efaf36ed893

[rio][fidl] Align RIO Description with FIDL2

This change eases the FIDL2 conversion by ensuring
that regardless of which protocol a client/server may
be speaking, objects will at least openable regardless.

ZX-1697 #done

Change-Id: I3197e9dbe00d2469618d55968e76696210a15c39

[fdio] Use ZXRIO_ON_OPEN unsolicited requests for open

- The zxrio_describe_t object replaces the zxrio_object_t
with a FIDL2 compatible format.
- Flip the usage of ZX_FS_FLAG_PIPELINE to be implied by
default. "ZX_FS_FLAG_DESCRIBE" may be used to request a
description object.
- ZXRIO_DESCRIBE can be trivially implemented using the
description object -- it currently isn't, because there
would be no clients through RIO.

ZX-1360 #comment In Progress

Change-Id: I1c7cad185af468b26c770dfd092382814a436c04

[fs] Use the Fuchsia-defined open flags

Re-lands 2aff2cba029cf0f7e98e6d19f6dc7a663c318227

This change uses the Fuchsia-defined flags on the wire
as well as on filesystem servers. Clients interacting
with filesystems through the POSIX compatibility layer
can continue using POSIX open flags; they will be translated
by the RIO layers client-side.

ZX-1359 #comment In Progress

Change-Id: I4972c024547a0daa2146831e49e34d3ef905d4b4

Revert "[fs] Use the Fuchsia-defined open flags"

This reverts commit 2aff2cba029cf0f7e98e6d19f6dc7a663c318227.

Reason for revert: Fuchsia uses upstream Rust, which doesn't pull these constants from our C library, but their own. I'll need to wait a few days for us to update upstream Rust before we can make progress here.

Original change's description:
> [fs] Use the Fuchsia-defined open flags
>
> This change uses the Fuchsia-defined flags on the wire
> as well as on filesystem servers. Clients interacting
> with filesystems through the POSIX compatibility layer
> can continue using POSIX open flags; they will be translated
> by the RIO layers client-side.
>
> ZX-1359 #comment In Progress
>
> Change-Id: I27dfdea2024183d5d59daa1ed7d8886d89d503d0

TBR=kulakowski@google.com,smklein@google.com,swetland@google.com,mcgrathr@google.com,planders@google.com

Change-Id: If93c2da36f92ea28ed013a61c01c6ec521da26cc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true

[fs] Use the Fuchsia-defined open flags

This change uses the Fuchsia-defined flags on the wire
as well as on filesystem servers. Clients interacting
with filesystems through the POSIX compatibility layer
can continue using POSIX open flags; they will be translated
by the RIO layers client-side.

ZX-1359 #comment In Progress

Change-Id: I27dfdea2024183d5d59daa1ed7d8886d89d503d0

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94