Fix [FD-43836] PATCH of purchase_cost for assets for comma as decimal separator

[uberbrady]

A customer who was using the "1.234,56" number format was having problems doing a PATCH of the purchase_cost for assets.

When he tried to pass "12,34" he got an error that a number was required. When he used an actual float, as in {"purchase_cost": 12.34} - the period got stripped out and the value was changed to 1234.00.

We already do some magic on creating new assets to allow for this. But we were not doing the same magic when doing a PATCH for an existing asset.

I also decided - and maybe this is me getting a little ahead of myself - that if you actually pass in an actual Float via JSON, then that Float is probably what you wanted. That change is a little bit scarier (to me), since it changes the setPurchaseCost mutator in SnipeModel.

I added in some tests for the PATCH method for US and EU formats, for string-numbers and real floats, making sure they still work as expected.

[what-the-diff]

PR Summary

• Incorporated relevant application model in UpdateAssetRequest.php
  The update asset request file now makes use of the Setting model in our application. This means that it can now directly interact with application settings related aspects more efficiently.

• Added conditional parameters in the rules() method
  This change has been applied to the UpdateAssetRequest.php file. This supports more precise evaluation of conditions when an asset update request is created.

• Enhancement to the setPurchaseCostAttribute() method
  Modifications were made to the SnipeModel.php file, specifically enhancing the setPurchaseCostAttribute() method. This allows for a more rigorous assignment of purchase costs to assets.

• New test-cases for updating Purchase Cost
  Several test-cases have been added to the UpdateAssetTest.php file. These were specifically designed to test the new and improved asset update request handling, particularly focusing on the purchase cost updating functionality. This will aid us in ensuring our new features work as expected.