[syscalls] Change vmar_... calls

- Create zx_vm_option_t type
- Change ZX_VM_FLAG_... to ZX_VM_... and make them new type.
- Change int32_t flags parameters to zx_vm_option_t options
- Make the options parameter be second.

- Modify vmar_..._old functions to keep other repos working.
Once they've all been updated these functions will go away.

ZX-2264
Test:CQ

Change-Id: I1faf4cc4e1e4dabf3d8ef680e398d83a545b0f09

[docs] Document VMAR lifecycle

Change-Id: I718df57fd47b7513c63a7fd5f49da0b464d4d0e3

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[docs] "user-space" -> "userspace"

Make all the usage consistent with the majority of the existing text.

Change-Id: I74bd431122ebbcd139c2a66477700000480b2912

[docs][errors] Rename all the errors in docs/ to MX_OK and MX_ERR_*

Change-Id: I62451456a83145760c6454a619d4c699ce8e9017

[docs] Add objects.md and objects/foo.md pages

Change-Id: I95b6a42330f8b9d3711c5c894aeaf88a9256f2de

[docs][vmar] Add VMAR object documentation

This also includes an example usage of the objects to make guard pages.

Change-Id: Ia77847dfd35f43329f652060f3a2018438041f9d

[vm] Implement new VM Address Region syscall interface

For compatibility, allow passing a process handle instead of a VMAR
to the vmar_map/unmap/protect calls and add usermode shims that
translate the old syscalls into the new ones.

Change-Id: I9ba29921d45f47d0d068e46e113dac1d139fce52