RCAL-467: Implement tests for Roman's TweakReg and ModelContainer. (#655

)

* Clean up and small refactorings.

* Raise exception when tweakreg_catalog is missing.

* WIP: unit tests.

* TweakReg unit test.

* Remove unused imports.

* Refactor tweakreg unit tests.

* Add description to unit tests.

* Refactored WCS generator for unit test.

* Deleted unnecessary data.

* Test refactoring.

* Fix style issue.

* Fix bug when testing save abs_refcat.

* Add another unit test.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix style to comply with new max line length.

* Add new unit test and general clean up.

* Add a comment about the unit for shift parameters.

* Fix typing issue.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* RCAL-482 (#658)

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Co-authored-by: Nadia Dencheva <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: William Jamieson <[email protected]>