add load method to Hdf5AmiciHistory

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 33.33333% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 84.53%. Comparing base (ccc7f72) to head (bf49e78).

Files	Patch %	Lines
pypesto/history/amici.py	33.33%	4 Missing :warning:

:exclamation: Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #1370 +/- ## =========================================== - Coverage 84.55% 84.53% -0.02% =========================================== Files 157 157 Lines 12949 12955 +6 =========================================== + Hits 10949 10952 +3 - Misses 2000 2003 +3 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.