fix(playout): improve the way hashlib is called in libretime_playout/player (#3135)

### Description

Improves the way hashlib is called in libretime_playout/player so that
is isn't broken on systems with python < 3.9

The way it is currently called in
site-packages/libretime_playout/player/file.py, in the section where
scheduled files are copied to the cache dir for playout, specifies the
usedforsecurity=False flag as follows:
`hasher = hashlib.md5(usedforsecurity=False)`

hashlib.md5 did not support this flag until Python 3.9. Attempting to
specify the flag directly as an argument to hashlib.md5(), in an older
python environment (such as that in Ubuntu Focal 20.04), is unsafe, and
can cause hashlib.md5() to balk/throw an exception, which results in
file copy operations failing. This then precipitates into playout
problems, as scheduled media is missing from the cache folder.


This PR instead calls using hashlib.new(), and passes the argument to
that, as follows:
`hasher = hashlib.new('md5', usedforsecurity=False)`

This method of calling with the flag argument is safer, because the
constructor will take it or leave it gracefully, regardless of whether
the system has a version of hashlib that supports the `usedforsecurity`
flag. AFAICT, it improves (fixes) function on older systems without
negatively impacting others.

### Testing Notes

**What I did:**
Before applying this patch, we were experiencing occasional but fairly
regular periods of silence when the system was supposed to be playing a
song or track. This behavior was consistent with errors such as the
following being present in the playout log:
```
2025-01-15 14:01:28,331 | INFO     | libretime_playout.player.file:copy_file:47 - copying file 19834 to cache /var/lib/libretime/playout/scheduler/19834.mp3
2025-01-15 14:01:28,466 | ERROR    | libretime_playout.player.file:copy_file:77 - could not copy file 19834 to /var/lib/libretime/playout/scheduler/19834.mp3: 'usedforsecurity' is an invalid keyword argument for openssl_md5()
Traceback (most recent call last):
  File "/opt/libretime/lib/python3.8/site-packages/libretime_playout/player/file.py", line 70, in copy_file
    file_event.filesize = self.report_file_size_and_md5_to_api(
  File "/opt/libretime/lib/python3.8/site-packages/libretime_playout/player/file.py", line 89, in report_file_size_and_md5_to_api
    hasher = hashlib.md5(usedforsecurity=False)
TypeError: 'usedforsecurity' is an invalid keyword argument for openssl_md5()
```
_For more information about the characterization and results of this
problem, see issue #3134_

**Testing on running systems**
After the patch was applied, these errors were no longer seen. I first
tested this on a dev server, and then on a live server, with
approximately 100 distinct tracks of playout occurring over about 24
hours. There were no file copy failures, and no related playout
problems, which was a major and immediate improvement.

**Testing installer, fresh installs**
***Ubuntu 20.04***
I deployed a patch to the installer and installed it on a blank system
running Ubuntu 20.04 and tested it to make sure the fix was applied and
worked.

***Debian 11***
I deployed patch to the installer and installed it on a blank system
running Debian Bullseye (which runs python = 3.9) , and tested it there
to make sure it did not break anything or introduce a regression.


### **Links**

Closes: #3134

playout/libretime_playout/player/file.py

@@ -86,7 +86,7 @@ class PypoFile(Thread):
             file_size = os.path.getsize(file_path)
 
             with open(file_path, "rb") as file_fd:
-                hasher = hashlib.md5(usedforsecurity=False)
+                hasher = hashlib.new("md5", usedforsecurity=False)
                 while True:
                     data = file_fd.read(8192)
                     if not data: