[Vertex AI] Add APIConfig to support switching to the Developer API
#1010
| Job | Run time |
|---|---|
| 1m 8s | |
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| 9m 22s | |
| 8m 28s | |
| 3m 8s | |
| 5m 51s | |
| 3m 21s | |
| 3m 36s | |
| 3m 48s | |
| 2m 11s | |
| 2m 40s | |
| 2m 28s | |
| 2m 5s | |
| 3m 19s | |
| 1m 57s | |
| 3m 28s | |
| 1h 6m 32s |