Prepare API layer for merged staking view

[buberdds]

I will stop here because there is something wrong with designs.

• account can stake to a validator multiple times and delegations endpoint will return one row - view is Ok in this case
• account can start debonding multiple times from a validator. We can have multiple rows (one row per epoch)
• What Shares column represents? summing delegation_shares + debonding_delegation shares doesn't make sense (since these are actually different shares)

Impl details:

• we won't have a dedicated endpoint to show Staking card so we need data from delegations and debonding_delegations
• https://nexus.oasis.io/v1/consensus/accounts/oasis1qqnk4au603zs94k0d0n7c0hkx8t4p6r87s60axru/delegations
• https://nexus.oasis.io/v1/consensus/accounts/oasis1qqnk4au603zs94k0d0n7c0hkx8t4p6r87s60axru/debonding_delegations
• [x] group debonding_delegations by validator and sum shares and amounts
• [ ] merge delegations and debonding_delegations group by validator and return custom object with props amount, debondingAmount, delegator,validator, debondingEpochs, shares(???)
• [ ] as we are losing backend pagination we will use frontend pagination
• [ ] ignore is_total_count_clipped for both endpoints
• [ ] add additional variant to Delegations table component

Alternatives:

• add badges in the right top header of Staking card (Active, Debonding) instead of (How shares are calc link) and show whatever endpoints provide in both sub views
• show Staking as two tabs next to Transfers, Evetns etc and show whatever endpoints provide

[github-actions[bot]]

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[buberdds]

we will go with https://github.com/oasisprotocol/explorer/pull/1461