fix: validate Product Bundle for existing transactions before deletion

[AfshanKhan]

Problem

The user can delete Product Bundles even if a transaction exists against them.

Steps to replicate

1. Create a Product Bundle.
2. Create a Sales Invoice with the Item as the Product Bundle.
3. Now delete the Product Bundle.

Enhancement

Now there is a validation to check if any transaction exists for the product bundle and the following message is displayed to the user when they try deleting any Product Bundle.

[deepeshgarg007]

We should also provide a disable checkbox similar to item master to disable any specific product bundle

[coveralls]

Coverage decreased (-0.05%) to 42.722% when pulling 100032a on AfshanKhan:validate-product-bundle-deletion into ac0bc1f on frappe:develop.