Add distribute_excess_idle

[sentilesdal]

Resolved Issues

Description

Adds distribute_excess_idle and all the helpers needed for it. Here's the full list:

• calculate_distribute_excess_idle
• calculate_distribute_excess_idle_share_proceeds
• calculate_distribute_express_idle_withdrawal_shares_redeemed
• should_short_circuit_distribute_excess_idle_share_proceeds
• calculate_distribute_excess_idle_share_proceeds_net_long_edge_case
• calculate_max_share_reserves_delta

explicit tests were added:

• fuzz_test_calculate_distribute_excess_idle
• fuzz_test_calculate_distribute_excess_idle_withdrawal_shares_redeemed
• fuzz_test_should_short_circuit_distribute_excess_idle_share_proceeds
• fuzz_test_calculate_distribute_excess_idle_share_proceeds_net_long_edge_case

Everything should be covered by the first test, but the others helped me debug along the way.

Review Checklists

Please check each item before approving the pull request. While going
through the checklist, it is recommended to leave comments on items that are
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• Testing
  • Are there new or updated unit or integration tests?
  • Do the tests cover the happy paths?
  • Do the tests cover the unhappy paths?
  • Are there an adequate number of fuzz tests to ensure that we are
    covering the full input space?
  • If matching Solidity behavior, are there differential fuzz tests that
    ensure that Rust matches Solidity?

[jalextowle]

It's looking good. Just a few more comments.