[Bug]: PYTHONPATH translation to sys.path fails if not single folder.

[reformstudios]

✈ Pre-Flight checks

• I don't have SentinelOne antivirus installed (see above for the solution)
• I have searched in the issues (open and closed) but couldn't find a similar issue
• I have searched in the pyRevit Forum for similar issues
• I already followed the installation troubleshooting guide thoroughly
• I am using the latest pyRevit Version

🐞 Describe the bug

pyRevit/dev/pyRevitLabs.PyRevit.Runtime/CPythonEngine.cs

Lines 201 to 206 in 9866e6f

	// manually add PYTHONPATH since we are overwriting the sys paths
	var pythonPath = Environment.GetEnvironmentVariable("PYTHONPATH");
	if (!string.IsNullOrEmpty(pythonPath))
	{
	sysPaths.Append(new PyString(pythonPath));
	}

PYTHONPATH is treated as a single path, rather than a list of paths.
It should be converted to sys,path as a list of paths, not a single path.
This prevents users from being able to define multiple external dependencies for pyrevit applications at runtime (eg when revit launches).

⌨ Error/Debug Message

n/a

♻️ To Reproduce

1. From shell, set pythonpath to multiple folders ; eg $env:PYTHONPATH="/path/a;/path/b"
2. launch revit
3. Launch script that attempts to import module in either path.
4. Observe import failing.

⏲️ Expected behavior

Pyrevit should initialise with existing PYTHONPATH being translated correctly to sys.path entries where PYTHONPATH is a list of folders not just a single folder.

🖥️ Hardware and Software Setup (please complete the following information)

n/a

Additional context

This is in the context of a VFX studio where python environment are defined prior to launching DCCs using PYTHONPATH with all dependencies added (typically using the "Rez" package manager).