[Bug] is_incremental always return False when use Project Number instead of Project ID

### Is this a new bug in dbt-bigquery?

- [X] I believe this is a new bug in dbt-bigquery
- [X] I have searched the existing issues, and I could not find an existing issue for this bug

### Current Behavior

Maybe relate dbt-labs/dbt-bigquery#1120 but I don't have confidence. It seems same phenomenon.

I use profile as Project Number and it's working properly without incremental model.

But when I use incremental model, this model alway create table if real table exists.

I notice this behavior is related to cache because it's working when I append --no-populate-cache flag

### Expected Behavior

I have three ideas of expected behaviors but I can't decide which is better

1. reject config project as Project Number
2. fix around cache method when use Project Number
3. Add some document to use Project ID

### Steps To Reproduce

1. use profile project as Project Number
2. create increment model and run twice
3. add --no-populate-cache and run

### Relevant log output

```shell
Nothing
```

### Environment

```markdown
- OS: Mac
- Python: 3.11
- dbt-core: 1.8.4
- dbt-bigquery: 1.8.2

I can reproduce
dbt-core: 1.7.7
dbt-bigquery: 1.7.4
```

### Additional Context

Nothing