Document default permission modes for file module

[bobrik]

What does this PR do?

Documents default permission modes for file module.

What issues does this PR fix or reference?

• file.managed and file mode don't mention default mode #39482

[cachedout]

Hmm, I wonder if a better and more accurate way to put this would be that the default permissions correspond to the umask of the user under which Salt is running.

[bobrik]

Just to confirm, is this what you are proposing?

Instead of this:

• The default mode for files is 0644.

You suggest something like this (I added more details for clarity):

• The default mode for new files corresponds umask of salt process. For existing files it's not enforced.

[cachedout]

@bobrik Correct.

[bobrik]

Updated. I used the same universal paragraph everywhere to make it easier to find and change.

[cachedout]

Thanks, @bobrik !