[FR] Add Entry Fulfillment as Type for Fulfillment Message DF Output

[kmaphoenix]

Is your proposal related to a problem?

When using the SearchUtil.get_agent_fulfillment_messsage_df method, it's not immediately evident when a fulfillment message comes from the Entry Fulfillment portion of a page.
With all of the other Fulfillment types, you can track them to an Event, Intent, Condition, or Intent+Condition route.

Describe the solution you'd like

Add entry_fulfillment as type for the output of this df:
https://github.com/GoogleCloudPlatform/dfcx-scrapi/blob/main/src/dfcx_scrapi/tools/search_util.py#L730

Additional context

Motivation is so that users can modify fulfillments in Google Sheets, then push those results back to Dialogflow CX when they have been updated.
On the "push back to CX" stage, it's important to know exactly where this fulfillment needs to be updated.