Rename storage level variables

[datejada]

Description

Rename variables so they align with the current standard in storage formulations:

In general: ``*_over_clustered_yeartointer_period`

Variables

• storage_level_over_clustered_year -> storage_level_inter_period

Constraints

• balance_storage_over_clustered_year -> balance_storage_intra_period

• max_storage_level_over_clustered_year_limit -> max_storage_level_inter_period_limit

• min_storage_level_over_clustered_year_limit -> min_storage_level_inter_period_limit

• max_energy_over_clustered_year -> max_energy_inter_period

• min_energy_over_clustered_year -> min_energy_inter_period