`prefix` keyword in `gta.psmap` is never applied

[HealthyPear]

Describe the bug

The prefix keyword in gta.psmap is never applied

To Reproduce

run the method on different ROI states and you always get the same files overwriting each other

PSmap_countspectrum.png
PSmap_ps_hist_sigma.png
PSmap_psmap_sigma.png
PSmap_psmap.png
PSmap.fits

Expected behavior

It should work in the same way as for gta.tsmap and gta.residmap.

Environment (please complete the following information):

• OS: (e.g. MacOS Monterey version 12.3.1) 15.7.1

• fermipy, fermitools, and fermitools-data versions (for exameple, fermipy 1.0.1, fermitools 2.0.8) fermipy 1.4.0