Resolve "Incoming deprecations"

Summary

Swap out all deprecated extern code

Explain your context

(Explain what you did.)

Please list breaking changes, new features or bugfixes

• Breaking Changes:

  • set minimum python verstion to 3.9.2

• Bugfixes:

  • renamed "fillna" to "ffill"
  • import "Callable" from collections.abc instead of typing
  • use python's deprecated decorator instead of own
  • opcua methods
  • utcnow

Closes #279 (closed)