fix(drive-abci): don't add up bytes for the same epochindex

[ogabrielides]

Issue being fixed or feature implemented

Strategy test run_chain_insert_many_new_identity_per_block_many_document_insertions_updates_and_deletions_with_epoch_change panickes with integer overflow when executed with 70+ blocks (default was 30: explanation why test isn't failing).

Function combine_non_base_epoch_bytes for each epoch was adding up the same value resulting into a geometrical growth of added_bytes.
combine_non_base_epoch_bytes: self:{2: 31} & rhs:{2: 31} -> {2: 62}
combine_non_base_epoch_bytes: self:{2: 62} & rhs:{2: 62} -> {2: 124}
...

What was done?

combine_non_base_epoch_bytes was updated to keep the value of bytes from rhs epoch_index_map for each corresponding epoch instead.
Updated behavior:
combine_non_base_epoch_bytes: self:{2: 21} & rhs:{2: 21} -> {2: 21}

How Has This Been Tested?

With this fix, the same test succeeds for 1000 blocks.

Breaking Changes

not sure if this is breaking change

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have added "!" to the title and described breaking changes in the corresponding section if my code contains any
• I have made corresponding changes to the documentation if needed

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone

[ogabrielides]

closing as the fix is done in grovedb