Fix discounts resolver to work like in docs

[tomaszszymanski129]

I want to merge this change because it fixes discounts resolver to work like in docs
more context: https://linear.app/saleor/issue/SHOPX-325/bug-discounts-field-behaviour-on-calculatetaxes-event-is-inconsistent

⚠️ This is a port of #15863

Impact

• New migrations
• New/Updated API fields or mutations
• Deprecated API fields or mutations
• Removed API types, fields, or mutations

Docs

• Link to documentation:

Pull Request Checklist

• Privileged queries and mutations are either absent or guarded by proper permission checks
• Database queries are optimized and the number of queries is constant
• Database migrations are either absent or optimized for zero downtime
• The changes are covered by test cases
• All new fields/inputs/mutations have proper labels added (ADDED_IN_X, PREVIEW_FEATURE, etc.)
• All migrations have proper dependencies
• All indexes are added concurrently in migrations
• All RunSql and RunPython migrations have revert option defined

[db-queries]

Here is the report for 3bb5600 (saleor:fix-discounts-resolver-317)
Missing base report (ec3e070). The results couldn't be compared.

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