ENH: add all hooks required to allow transition of pytmc stcmd -> template

[klauer]

Context

Related: https://github.com/pcdshub/pytmc/issues/209 Pairs with: https://github.com/pcdshub/ads-ioc/pull/86

Changes

• Adds helper commands to pytmc template, which can be used in Jinja templates:
  • generate_records (create .db and .archive files)
  • get_plc_by_name
  • get_symbols_by_type
• Adds variables to pytmc template environment, which can be used in Jinja templates:
  • pytmc_version
• Adds --macro option to pytmc template
• Fixes some annotations + uncovered/untested functionality
• Need for separate pytmc stcmd and pytmc db step goes away
  • Either can still exist if desirable, but ads-ioc will only use pytmc template for the main build step
• Allows pytmc template to read/write multiple templates with parsing a project only once

[klauer]

(I mistook the above for approval, sorry @ZLLentz. I'm going to add branch protection now)

[ZLLentz]

I'll hit a quick post-review

[ZLLentz]

Everything looks fine- I didn't follow all the paths but nothing super weird, I'm going to focus on other PRs