Fix wonky writing to sarif_file

[Qalthos]

Fixes #4349

We're misusing Path.open() to look like we're using pathlib when we're effectively calling open(sarif_file) with more steps. The problem is that somewhere, sarif_file is getting picked up as AnsibleUnicode, which passes through Path.open when provided in place of the path object, but not in Python 3.10, where Path.open() is less straightforward in its implementation.

This fixes the issue, but does not solve the underlying problem, which is that Options.sarif_file is typed as a Path, but appears to take the value of a string. Either Options needs to be fixed to return this as a Path or the type should be fixed.

The change from open() -> write() to write_text() is not strictly related but looks a lot cleaner and forces the inconsistent usage to be an error.