refactor(qc): remove `ScalarCondition::[Not]InTemplate` (#5735)
Remove `ScalarCondition::InTemplate` and `ScalarCondition::NotInTemplate` and instead add placeholders as the third variant in `ConditionListValue`. This simplifies the implementation and makes some illegal states unrepresentable (previously it was possible to construct `ScalarCondition::InTemplate`/`ScalarCondition::NotInTemplate` with arbitrary `PrismaValue`s and with field references).