[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

[sync] Apply C API rubric to libsync

Test: No behavior change
Change-Id: I30a413f7fb5d3f4e741e5204532b82e73595c086

[nandpart] Fix intialization bug

Caught while testing under ASAN.

Change-Id: Ibaf0a105f044209f31be01b5e1bb30c468dc7220
Tested: Ran nandpart-test while built with ASAN enabled.

[zx] Migrate libzx off legacy_unowned<T> and update call-sites.

- Migrate APIs like zx::process::self() from returning a
|const zx::legacy_unowned<T>| to returning |zx::unowned<T>|.
- Update callers of those APIs to use the appropriate dereference
operator to access members of T, or to get a |const T&| to pass to
libzx-wrapped syscalls.
- Remove the zx::legacy_unowned<T> template.

Bug: ZX-2310
TEST=CQ
Change-Id: Idd4267cd0246ec9ab0e6f1392efe7fda45ff169d

[dev][nandpart][bad-block] Implement bad-block protocol.

bad-block protocol implementation is specific to the methodology used
in the AML u-boot bootloader. We preserve the same semantics so as to
allow the bootloader to continue to read the system partitions even
after additional bad blocks have been grown.

Change-Id: I37954fccf67822459f9c7522c0299a5568c65fb1
Tested: TODO