bulkWrite operations on any sharded collection are completely broken in 8.4.1+

[adf0nt3s]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

8.3.4

Node.js version

18.20.4

MongoDB server version

6.x

Typescript version (if applicable)

5.4.5

Description

buildBulkWriteOperations adds the shard key to the filter condition, but it sets it to the schema's value, not the document's value. The test that covers this bit of logic passed because it wasn't really using an updated shard key value

Steps to Reproduce

I've opened a PR here. The test i adjusted will fail with the current logic

For convenience, i've pasted the test below

    it('builds write operations', async() => {

      const userSchema = new Schema({
        name: { type: String },
        a: { type: Number }
      }, { shardKey: { a: 1 } });

      const User = db.model('User', userSchema);

      const users = [
        new User({ name: 'Hafez1_gh-9673-1', a: 1 }),
        new User({ name: 'Hafez2_gh-9673-1', a: 2 }),
        new User({ name: 'I am the third name', a: 3 })
      ];

      await users[2].save();
      users[2].name = 'I am the updated third name';

      const writeOperations = User.buildBulkWriteOperations(users);

      const desiredWriteOperations = [
        { insertOne: { document: users[0] } },
        { insertOne: { document: users[1] } },
        { updateOne: { filter: { _id: users[2]._id, a: 3 }, update: { $set: { name: 'I am the updated third name' } } } }
      ];

      assert.deepEqual(
        writeOperations,
        desiredWriteOperations
      );

    });

Expected Behavior

No response