fc_util: remove unnecessary `pub`s from functions
fc_util: remove unnecessary `pub`s from functions

* moved functions used only by the unit tests in the tests module
* removed the `pub` attribute from said functions; the items that remain
  `pub` are imported/used in other modules and need to stay `pub`

Signed-off-by: Alexandra Iordache <750ec4522de000f31ad44d64614ad5747f238032@amazon.com>

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