Add CTF phase retrieval to preprocessers

[deding2000]

Description

The Paganin processor is already implemented in CIL and can provide good phase contrast and/or work as a filter which improves the SNR. In certain cases, however, the contrast transfer function (CTF) can provide higher resolution under the assumption of a weakly absorbing object with slowly varying phase

Environment

import cil, sys
print(cil.version.version, cil.version.commit_hash, sys.version, sys.platform)

Python 3.9.25 (main, Nov 10 2025, 00:00:00)
[GCC 11.5.0 20240719 (Red Hat 11.5.0-11)] on linux