Summary data saved to storage with ert<8.4 is loaded as float64

[eivindjahren]

This can be reproduced by removing the astype(np.float32) from the following line: https://github.com/equinor/ert/blob/0d1b285e0b88c70770ffad820cec1ccf02fe10a0/tests/integration_tests/test_storage_migration.py#L141

[oyvindeide]

We need to migrate storages from older versions by converting the summary data from float64 to float32. This problem occured originally because it was read in float32, but converted to float64 by resdata, and we just saved what we got.