Change Generator update_macros call to just update current macros

[OCopping]

This is instead of wiping out old dictionary with the updated_macros one.
This would cause issues if extra macros were defined in techui-support.yaml for the screen that are not a part of the prefix, as they would be cleared. An example of which is for the multipositioner embed screen.

  positioner.multipositioner:
    prefix: "{{ P }}"
    macros:
      - P
      - MP
    screens:
      - file: positioner/positioner_embed.bob
        type: embedded

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.04%. Comparing base (7f9a915) to head (294e221).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #261   +/-   ##
=======================================
  Coverage   96.03%   96.04%           
=======================================
  Files          13       13           
  Lines         984      985    +1     
=======================================
+ Hits          945      946    +1     
  Misses         39       39           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.