Utils: add source locators (#2496)

* Cat: add source locators

* make test handle both cases

* test that the wrong source locator is not included for Cat

* Add source locators to FillInterleaved and test

* Add Bitwise Spec

* add FillSpec

* Reverse Spec

* Checkpoint -- doesn't compile

* Make source locators more correct with do_apply methods

* add source locators to Reg.scala

* RegEnable source locator tests

* ShiftRegisters source locators unit tests

* scalafmt

* clean up spacing and final defs

* scalafmt

* scaladoc groups