Add Firebase Data Connect v2 support

[lisajian]

Description

Adds basic FDC function trigger for onMutationExecuted

Includes unit tests, but missing integration tests, which will be included in a subsequent PR once the backend changes are completed. Also fixes a typo on an existing file

npm test passes locally

Internal tracking bug: b/436623435

Code sample

Examples of how to use this

import { onMutationExecuted } from "firebase-functions/v2/dataconnect";

exports.myfunction = onMutationExecuted(
  {
    service: "service-id",
    connector: "connector-id",
    operation: "mutation-name",
  },
  (event) => { 
    // event.params.service == "service-id" 
    // event.params.connector == "connector-id"
    // event.params.operation == "mutation-name"

    // event.data contains [MutationEventData](https://docs.google.com/document/d/1sCYuBzjhirVTy9Xo2gflGVcKcZyhau9MhkVlbOvC4MI/edit?tab=t.0#bookmark=id.1k7sz3vu87vx)  
  }
);

// Use capture group on operation
exports.myfunctionwithcaptures = onMutationExecuted(
  {
    service: "service-id",
    connector: "connector-id",
    operation: "{operation}",
  },
  (event) => { /** do something */ }
);

// Use wildcard on connector
exports.myfunctionwithwildcards = onMutationExecuted(
  {
    service: "service-id",
    connector: "*",
    operation: "mutation-name",
  },
  (event) => { /** do something */ }
);

See go/fdc-eventarc-functions-sdk for more information

[taeold]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces support for Firebase Data Connect v2 with the onMutationExecuted trigger. The changes are well-structured, including the new provider, unit tests, and necessary package configuration updates. I've identified a few type safety issues in the new provider implementation concerning the handling of optional parameters, which could lead to runtime errors. I've provided suggestions to address these. Additionally, I've included a recommendation for a minor refactoring to enhance code clarity.