pytmc template filename usage awkward on Windows

[klauer]

os.pathsep is currently used to delimit the input file and the output file:

pytmc/pytmc/bin/template.py

Line 714 in 20d35b3

input_filename, output_filename = template.split(os.pathsep, 1)

This is : on Linux and ; on Windows.
Our ads-ioc Makefile only uses : (https://github.com/pcdshub/ads-ioc/blob/fc8a48a586751be00ba62b79c3a6cac7aface529/iocBoot/templates/Makefile.base#L101)

This is used with ads-deploy in Visual Studio, resulting in something like:

	--template "c:/Repos/ads-ioc/R0.6.0//iocBoot/templates/st.cmd.template":"st.cmd" \

My thought as to a fix:

I think we should standardize on : for all platforms.
On Windows, we can iteratively check for the longest match that is an existing file. The remainder is the output.
It'll be easier for us and users in the end... probably?

For now, this is patched locally/temporarily on plcprog-console