fix: close file gracefully in espsecure (ESPTOOL-804)

[gnought]

The espsecure.py script displays a ResourceWarning error regarding unclosed files when PYTHONWARNINGS="all" turns on. This issue arises because espsecure.py utilizes argparse.FileType, which opens a file handler but Python does not automatically handle the close() operation.

% PYTHONWARNINGS="all" espsecure.py sign_data --version 1 --keyfile keys.pem  --output signed.bin input.bin
espsecure.py v4.7.0
Signed 1032336 bytes of data from input.bin
/dev/.venv/lib/python3.11/site-packages/espsecure/__init__.py:1828: ResourceWarning: unclosed file <_io.BufferedReader name='keys.pem'>
  main()
ResourceWarning: Enable tracemalloc to get the object allocation traceback
/dev/.venv/lib/python3.11/site-packages/espsecure/__init__.py:1828: ResourceWarning: unclosed file <_io.BufferedReader name='input.bin'>
  main()
ResourceWarning: Enable tracemalloc to get the object allocation traceback

This fix is to handle the close() explicitly to have a gracefully exit and avoid memory leaks.

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[Honza0297]

Hello, @gnought, thank you for the contribution!

Everything looks good to me, just one nitpick: can you please squash your commits into one?

[gnought]

@Honza0297 sure, here you go.

[Honza0297]

Thank you!
We will merge it once it goes through our pipeline.

[radimkarnis]

Thank you for your contribution!