Leaderboard page should display Top 10 Accounts by balance for each coin

Business/User Value: As an Explorer of Diem I want to who owns the most coins so that I don't have to use a CLI to get this info

### Acceptance Criteria
**GIVEN** I am on the Leaderboard page
**THEN** I see a table with the Top 10 accounts ordered by balance for each coin

**DESIGN NOTES**
The tables should display:
* Rank
* Address (as a link)
* Amount

**DEV NOTES**
* Just do XUS for now
* **The query to get this data currently takes way too long.**
* Consider creating a view to simplify the query
* Also consider adding an index on balance to improve query performance
* Here's the queries we tried:
```GraphQL
accounts_balances(limit: 10, order_by: {balance: desc}, where: {currency: {_eq: "XUS"}}) {
address
balance
currency
timestamp
version
}
realtime_account_balances(limit: 10, order_by: {balance: desc}, where: {currency: {_eq: "XUS"}}) {
account
balance
blockchain_timestamp
currency
indexer_timestamp
version
}
```