Quote file paths in Teradata TPT shell commands and pass the openssl passphrase via stdin

[potiuk]

The Teradata provider's tpt_util.py and encryption_utils.py build several
shell commands (run locally or over SSH) that interpolate file paths directly,
and pass the openssl passphrase on the command line.

This hardens both:

• Quote interpolated file paths with shlex.quote() in the POSIX shell
  commands (shred, the dd/rm fallback, chmod, which, and the
  openssl … -in/-out paths), so paths containing spaces or shell
  metacharacters are handled correctly and cannot alter the command.
• Feed the openssl passphrase on stdin (-pass stdin) for the local
  generate_encrypted_file_with_openssl instead of -pass pass:<…>, so it is
  not exposed in the local host's process list.

Windows command branches and the remote SSH openssl -pass pass: path are left
unchanged (POSIX shlex.quote does not apply to cmd.exe, and moving the
passphrase off argv over the SSH channel would require reworking the shared
remote-exec helper — a larger change).

Tests

• existing command-string assertions still pass (metacharacter-free paths
  are unchanged by shlex.quote)
• new: shred / chmod commands quote paths with spaces / metacharacters
• new: the openssl passphrase is fed on stdin and never appears on argv

Was generative AI tooling used to co-author this PR?

• Yes — Claude Opus 4.8 (1M context)

Generated-by: Claude Opus 4.8 (1M context) following the guidelines at
https://github.com/apache/airflow/blob/main/contributing-docs/05_pull_requests.rst#gen-ai-assisted-contributions