Cli: inflation rewards Reward Slot no longer accurate for multiple accounts

[CriesofCarrots]

Problem

Now that the Partitioned Epoch Rewards feature is active, stake accounts receive their rewards across a range of slots, instead of all in the same slot. The RPC getInflationReward accepts multiple stake-account addresses and returns the correct effective slot for each account/reward. But the solana-cli assumes the effective slot for the first reward applies to all accounts queried (CliEpochRewardsMetadata::effective_slot). When --output json is passed, the return includes the correct effectiveSlot within each reward struct, but also includes an incorrect effectiveSlot at the top level.

Proposed Solution

Deprecate CliEpochRewardsMetadata::effective_slot
In human-readable mode, display Reward Slot in each reward line