bug: fix file_conversion disk leak (#3562)
Fix disk space leaks and Windows errors when accessing file.name on a
NamedTemporaryFile
Uses of `NamedTemporaryFile(..., delete=False)` and/or uses of
`file.name` of NamedTemporaryFile have been replaced with
TemporaryFileDirectory to avoid a known issue:
-
https://docs.python.org/3/library/tempfile.html#tempfile.NamedTemporaryFile
- https://github.com/Unstructured-IO/unstructured/issues/3390
The first 7 commits each address an individual occurrence of the issue
if reviewers want to review commit-by-commit.
