Fixed some static analysis warnings related to public constants

[PhantomGrazzler]

Changed to either private, or static readonly if they needed to stay public.

[github-actions[bot]]

Unit Test Results

       5 files         5 suites   24s :stopwatch: 1 387 tests 1 299 :heavy_check_mark:   88 :zzz: 0 :x: 2 602 runs  2 498 :heavy_check_mark: 104 :zzz: 0 :x:

Results for commit 4201dc54.

:recycle: This comment has been updated with latest results.

[milkshakeuk]

@PhantomGrazzler thanks for this!