[fbl] Remove libzx dependency from libfbl

Code that depends on the Zircon syscalls should be in fzl instead.
See <https://fuchsia.googlesource.com/zircon/+/master/docs/cxx.md#fzl>

Test: fzl-test
Change-Id: Ic65425fc51136edf4d401097f6b483d56923104e

[fbl] Add constexpr TypeInfo<T> to compute typenames at compile time.

fbl::TypeInfo<T>::Name() returns a statically allocated C-style string
name of type T for all types.

TEST=fbl-test passes.

Change-Id: I32bf5b5caaa6a045464b5c45a70438bb7457be0c

[fbl][vmo] Moving VmoMapper out of fbl

The VmoMapper and the VmarManager classes are more
of vmo utilities than fbl libraries. In preparation
for adding more such utilities, I am moving these libraries
to another location.

There are other CLs to update usage of this library in
the other repos.

Change-Id: I610bfd2838cf7843120d4aa885d24ea3b1b97b73

[build] introduce hosttest module type

These get installed in $(BUILDDIR)/tests but otherwise are
just like hostapp modules.

Update existing host tests to use this module type.

Change-Id: Ic981d98a28faaa16699967e6263ecac5044bafc8

[fbl] Add integer_sequence et al.

Adds an efficient integer_sequence and related templates similar
to those in std. These templates are useful for compile-time
manipulation of sequences and construction / evaluation of
positional types.

Change-Id: I665a8c697fbfa79abe1080145d58144f47973fd9

[tests] Add probe_for_read|write test helpers.

These allow testing whether a memory address is readable or writable.

ZX-1574

Change-Id: I630a0f6fb9177f14ab13918da7e5ec7ed2fc584f

[fbl] Add a "VmoMapper" utility class.

Add a small class which handles the process of creating a VMO of a
given size and mapping it into the local address space, as well as
automatically unmapping at end-of-life.

Change-Id: I10fba0ae90201a414a0a49eab4c77150081bec2c

[make] add DISABLE_FBL_TEST to disable building the fbl-test app

The fbl-test utest and host test app are responsible for nearly 1/3 of
the total compile time. Since it's not changing much, add a build system
switch to locally disable it.

add DISABLE_FBL_TEST:=true to local.mk or set it in the environment to
use.

Change-Id: Icc27cd67243149ded2181a3a1926d08751324b9d

[fbl] Add support for a scoped file descriptor

ZX-1304 #done

Change-Id: Ic622721a7b23d3f22b818612810941ca2ad61b7b

[fbl][string] Improve interoperability with std::strings.

Added template constructors to fbl::StringPiece and fbl::String which
accept a variety of string-like objects. This is intended to reduce
the pain of having multiple string representations floating around.

Use the new trait for the tracing API.

Change-Id: Id0c73d386f1286e1e91e94af295a311b80db311b

[zx] Rename bug references from MG-nnn to ZX-nnn

Change-Id: I07b0ee32bd7e8cc08e344896352c156b3b420349

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[zircon][mxtl->fbl] Rename mxtl to fbl

Change-Id: Ie21b6498e1bfb0a7fa0315e40b9e5c3ee78646be