Update MongoDbStore.cs

[sfmskywalker]

This pull request updates the MongoDbStore class in src/modules/persistence/Elsa.Persistence.MongoDb/Common/MongoDbStore.cs to enhance the UpdatePartialAsync method with additional functionality and improve error handling.

Enhancements to UpdatePartialAsync:

• Changed the return type of UpdatePartialAsync from Task to Task<bool> to indicate whether the update operation succeeded.
• Added a new throwIfNotFound parameter to UpdatePartialAsync, allowing callers to specify whether an exception should be thrown if no matching document is found.
• Implemented conditional logic based on throwIfNotFound to either throw an InvalidOperationException or return false when no document matches the provided ID.
• Modified the method to return true if the update modifies at least one document, or false otherwise.