Forkpty replace

[RoniKishner]

What this PR does / why we need it:

replace pexpect.spawn with pty+subprocess to avoid forkpty

• Replace pexpect.spawn with pty.openpty() + subprocess.Popen to avoid deprecated os.forkpty() in Python 3.12+ multi-threaded processes
• Add _spawn_console() to create a pty pair and wrap the subprocess in pexpect.fdpexpect.fdspawn
• Add _terminate_proc() to cleanly shut down the subprocess, call it in both the connect error path and disconnect cleanup
• Simplify console_eof_sampler() — remove parameters, use _spawn_console() internally

Which issue(s) this PR fixes:

DeprecationWarning on test_vm_console

Special notes for reviewer:

The following warning was shown:
/tmp/pr-tests/.local/share/uv/python/cpython-3.14.5-linux-x86_64-gnu/lib/python3.14/pty.py:66: DeprecationWarning: This process (pid=110) is multi-threaded, use of forkpty() may lead to deadlocks in the child.

jira-ticket:

NONE

[RoniKishner]

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[RoniKishner]

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Split complete. Open these pull requests:

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