[roll] Roll fuchsia [starnix] Implement TIOCGPTPEER ioctl in devpts

This implements the TIOCGPTPEER ioctl for primary PTYs. It allows safely
obtaining a replica PTY file descriptor without performing path lookup,
which is useful for avoiding race conditions and bypasses mount
namespace restrictions.

When opening /dev/ptmx, we record the replica's NamespaceNode on the
primary PTY file object directly. This allows TIOCGPTPEER to open a file
descriptor to the replica without performing path resolution.

Test: Added Pty.IoctlTIOCGPTPEER to terminal_test.cc.
Test: fx test fuchsia-pkg://fuchsia.com/starnix_syscalls_cpp_tests#meta/terminal_test.cm --test-filter "*IoctlTIOCGPTPEER*"
Original-Original-Fixed: 525046044
Original-Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1679056
Original-Original-Revision: 9992f2c5e95ed9cb4887ff18ca84503a50abe804
GitOrigin-RevId: 1fef9bd818e309f526b400ca4b7a70ee86db2b01
Change-Id: I1bce6402d88be2552b994a19bf43f21872025f8c
Reviewed-on: https://fuchsia-review.googlesource.com/c/integration/+/1697554
Cr-Commit-Position: refs/heads/main@{#196375}