[RFC] Remove Templates and move them to a separate repository

[jd-lara]

Templates have had a very limited use in PowerSimulations specially since there isn't a single agreed upon model of a DA or a Unit Commitment. Further, these templates are extremely hard to test on their own since they also require models that capture many devices.

This issue is to request comments and discussions to move the code related to moving the code in https://github.com/NREL-Sienna/PowerSimulations.jl/blob/main/src/operation/operation_problem_templates.jl to a separate repository similar to PowerSystemCase builder where we can maintain and document the templates separately.

It would be possible to even create templates for specific ISO's and extend the cases we want to support and run.

[rodrigomha]

One idea is to simply leave a StandardPCM template, that uses StandardUC for Thermal and things like that, but then move everything else to other repo, like other PowerSimulationsTemplates, that could have ED, AGC, and docs how to modify them.