[zx] Clean up some libzx container APIs, implementations, and callers.

- Add a zx::job::create() API accepting zx::job rather than zx_handle_t.
- Migrate all out-param handles to be output via reset_and_get_address().

Bug: ZX-2310
TEST=libzx-test
Change-Id: Ib9cb9a0778d8747f35996134038936d1f7bb3397

[interrupts][syscall] Rename syscalls zx_irq_* to zx_interrupt_*

Change-Id: Ie01f65f29c1fd6171463340e2a5c103ff8e704b6

[syscall][irq] Remove (disabled) old irq syscall implementations

Change-Id: I2f4a4f42e174dbab5ac4eb84255955fa805cd75d

[interrupt][syscalls] Adapt to new interrupt syscalls

ZX-2024
Change-Id: I534d4087d0dcf199ea38ced0fd2f0af98548b719

[zx] Move public zx headers to match naming convention

The zx library provides headers intended for general use, so the
include path should be spelled <lib/zx/foo.h> as per
https://fuchsia.googlesource.com/docs/+/master/development/languages/c-cpp/naming.md.
This moves the headers into the proper location and updates includes to
match.

Change-Id: I6fc9b2a491b5f8b0d270c4dfc77fa4be5739071b

[zx] Add zx::interrupt

This object type is needed by FIDL2.

Also, remove spurious pci reference from tests.fidl2.

Change-Id: I6ad44e349c30bb01c0f5d308aa3cee3107da29e0