Remove cmake switch for open source version

[ni-mheppner]

Clean up prior to making a new release version.

• Remove everything that is irrelevant in the context of the open source version
• Apply global cmake option for unity builds as proposed here

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (c7b0e9e) 83.10% compared to head (e63ad7f) 83.10%. Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #68 +/- ## ======================================= Coverage 83.10% 83.10% ======================================= Files 82 82 Lines 2024 2024 ======================================= Hits 1682 1682 Misses 342 342 ```

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