This fixes the discount_ calculation logic and promotion tax inclusiveness calculation (#12960)

* This fixes the discount_ calculation logic

* This fixes the adjustment to be handled as a subtotal value in every calculation and applies the tax inclusive logic on the promotion value itself

* Added some testcases and revoked some changes to improve testing output

* Fixed a test case based on feedback

* Corrected promotion/admin test cases

* Corrected cart/store test case

* Improved cart/store test cases for more robust promotion testing considering tax inclusion flags

* Remove unnessary changes as adjustments now automatically are subtotals and therefore the tax inclusive flag does not need to be applied again

* Remove adjustments->is_tax_inclusive usage everywhere

* Migration script to remove is_tax_inclusive in cart line item adjustment

* Forgot to adjust one more testcase

* Corrections based on fPolic feedback

* Refactored PR to consider feedback from oliver

* Added more testcases for promotion in cart

---------

Co-authored-by: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>

.changeset/pink-baboons-wash.md

@@ -0,0 +1,11 @@
+---
+"@medusajs/promotion": patch
+"@medusajs/core-flows": patch
+"integration-tests-http": patch
+"@medusajs/cart": patch
+"@medusajs/types": patch
+"@medusajs/utils": patch
+"@medusajs/medusa": patch
+---
+
+This fixes the discount\_ calculation logic and promotion tax inclusiveness calculation