updates for keras_core / multi-backend support
#406
| Job | Run time |
|---|---|
| 7m 39s | |
| 13m 0s | |
| 16m 11s | |
| 15m 24s | |
| 9m 43s | |
| 7m 56s | |
| 6m 30s | |
| 6m 24s | |
| 2m 16s | |
| 6m 12s | |
| 8m 15s | |
| 6m 50s | |
| 9m 40s | |
| 8m 49s | |
| 2h 4m 49s |