Upsert failed when the record is updated instead of inserting, using on tables with id of number type.

Issue description

Using queryRunner.manager.upsert() on tables whose id's type is number will result in error: Cannot update entity because entity id is not set in the entity.

Expected Behavior

The upsert runs successfully.

Actual Behavior

Error thrown: Cannot update entity because entity id is not set in the entity., in ReturningResultsEntityUpdator.insert()

const entityIds = entities.map((entity) => {
    const entityId = metadata.getEntityIdMap(entity);
    // We have to check for an empty `entityId` - if we don't, the query against the database
    // effectively drops the `where` clause entirely and the first record will be returned -
    // not what we want at all.
    if (!entityId) {
        throw new error_1.TypeORMError(`Cannot update entity because entity id is not set in the entity.`);
    }

    return entityId;
});

The upsert should run properly if the id's type is bigint, and fail with other types, since in ColumnMetadata.createValueMap(), it converts a field value to string if

this.generationStrategy === "increment" ||
this.generationStrategy === "rowid") &&
this.type === "bigint" &&
value !== null

The process update instead of inserting the record, so insert_id will be undefined. Hence, the upsert will not throw the aforementioned error if the id is of bigint type, as the id will appear as "undefined".

Steps to reproduce

Create a table Test with id as follow:

@PrimaryGeneratedColumn("increment")
id: number;

and a unique pair of keys

@Index(["key1", "key2"], { unique: true })
...
@Column()
key1: string;

@Column()
key2: string;

finally a value field for upserting: ... @Column() value: string;

Then just run `queryRunner.manager.upsert(Test, {key1: "a", key2: "b", value, "c"}, ["key1", "key2"])` (run 2 times if the record isn't in the table)


### My Environment

| Dependency          | Version  |
| ---                 | ---      |
| Operating System    | Windows         |
| Node.js version     |22.15.0  |
| Typescript version  | 5.7.2  |
| TypeORM version     | 0.3.20  |


### Additional Context

_No response_

### Relevant Database Driver(s)

- [ ] aurora-mysql
- [ ] aurora-postgres
- [ ] better-sqlite3
- [ ] cockroachdb
- [ ] cordova
- [ ] expo
- [ ] mongodb
- [x] mysql
- [ ] nativescript
- [ ] oracle
- [ ] postgres
- [ ] react-native
- [ ] sap
- [ ] spanner
- [ ] sqlite
- [ ] sqlite-abstract
- [ ] sqljs
- [ ] sqlserver

### Are you willing to resolve this issue by submitting a Pull Request?

No, I don’t have the time and I’m okay to wait for the community / maintainers to resolve this issue.