Preload celo_account on AddressReadProxyController when available.

[rkachowski]

Description

The application is crashing when trying to display data it has not loaded from the database (specifically celo epoch data). This PR adds an optional preload to the db fetch to include celo_accounts information should it exist for the address being fetched.

Tested

• tested locally against rc11 db
  • http://localhost:4011/address/0x4aAD04D41FD7fd495503731C5a2579e19054C432/read-proxy#address-tabs loads correctly without 500 error

Issues

• Fixes https://github.com/celo-org/data-services/issues/734

[github-actions]

Unit Test Results

       5 files  ±0     363 suites  ±0   3m 30s ⏱️ -2s
2 637 tests ±0  2 563 ✔️ ±0  74 💤 ±0  0 ❌ ±0 
2 651 runs  ±0  2 575 ✔️ ±0  76 💤 ±0  0 ❌ ±0 

Results for commit 1920124. ± Comparison against base commit 590d02e.