fix(nano): fix calls to get_balance on other contracts

[glevco]

Depends on #1406

Motivation

There's a bug when trying to get the balance of another contract when that contact is not part of the call chain. Since its changes tracker is not created, the Runner._get_balance will raise a KeyError. This PR fixes this and adds the missing tests.

Acceptance Criteria

• Fix Runner._get_balance so it can get the balance of other contracts. Getting the balance of another contract before the current call is not supported.
• Refactor Runner.get_current_changes_tracker so it doesn't take any arguments. It was always called with the current contract id.
• Add missing tests.

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[github-actions]

Bencher Report

Branch	fix/nano/another-balance
Testbed	ubuntu-22.04

🚨 1 Alert

Benchmark	Measure Units	View	Benchmark Result (Result Δ%)	Upper Boundary (Limit %)
sync-v2 (up to 20000 blocks)	Latency minutes (m)	📈 plot 🚷 threshold 🚨 alert (🔔)	2.11 m (+22.30%) Baseline: 1.72 m	2.07 m (101.92%)

Click to view all benchmark results

Benchmark	Latency	Benchmark Result minutes (m) (Result Δ%)	Lower Boundary minutes (m) (Limit %)	Upper Boundary minutes (m) (Limit %)
sync-v2 (up to 20000 blocks)	📈 view plot 🚷 view threshold 🚨 view alert (🔔)	2.11 m (+22.30%) Baseline: 1.72 m	1.55 m (73.59%)	2.07 m (101.92%)

🐰 View full continuous benchmarking report in Bencher

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.91%. Comparing base (2387a69) to head (990c958).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1452      +/-   ##
==========================================
- Coverage   86.03%   85.91%   -0.13%     
==========================================
  Files         434      434              
  Lines       33739    33740       +1     
  Branches     5291     5291              
==========================================
- Hits        29029    28987      -42     
- Misses       3673     3700      +27     
- Partials     1037     1053      +16     

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