fix(core-flows, types): export steps and types related to credit lines (#12567)

- Export steps that are used in credit-line related workflows
- Move workflow's input type to the `workflows.ts` type file
- Add and update TSDocs

.changeset/old-dancers-retire.md

@@ -0,0 +1,6 @@
+---
+"@medusajs/core-flows": patch
+"@medusajs/types": patch
+---
+
+fix(core-flows, types): export steps and types related to credit lines