testing: remove basics AccountData.OnlineAccountData conversion function

[cce]

Summary

We have a conversion function in the basics.AccountData type to make a basics.OnlineAccountData type, but it is only used by tests. The actual conversion used by non-test code occurs in ledgercore.AccountData. However tests continue to use this function for setting up small tests with fake accounts and mocked ledgers. This moves it to the data/basics/testing package to hopefully reduce confusion, and make it so non-test code will continue to not use this method.

Test Plan

Existing tests were updated and should still pass.

[Copilot]

Pull Request Overview

This PR moves the conversion function for AccountData to OnlineAccountData out of the production code and into the testing package, updating tests across the repository to use the new basics_testing.OnlineAccountData conversion function.

• Replaces all calls to ad.OnlineAccountData() with basics_testing.OnlineAccountData(ad) in test files.
• Removes the OnlineAccountData conversion function from the production data/basics/userBalance.go file and reintroduces it only for testing purposes in data/basics/testing.

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
ledger/ledger_test.go	Updated OnlineAccountData conversion function call in tests.
ledger/eval_simple_test.go	Updated OnlineAccountData conversion function call in tests.
ledger/eval/eval_test.go	Updated OnlineAccountData conversion function call in tests.
ledger/acctonline_test.go	Updated OnlineAccountData conversion function call in tests.
data/committee/common_test.go	Updated OnlineAccountData conversion function call in tests.
data/basics/userBalance_test.go	Removed extra helper functions; tests adjusted for new conversion.
data/basics/userBalance.go	Removed the OnlineAccountData conversion function from production.
data/basics/testing/userBalance_test.go	Added tests for the new testing conversion function.
data/basics/testing/userBalance.go	Introduced the OnlineAccountData conversion function for tests only.
agreement/fuzzer/ledger_test.go	Updated OnlineAccountData conversion function call in tests.
agreement/common_test.go	Updated OnlineAccountData conversion function call in tests.
agreement/agreementtest/simulate_test.go	Updated OnlineAccountData conversion function call in tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.57%. Comparing base (8341e41) to head (461f232).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6313      +/-   ##
==========================================
- Coverage   51.60%   51.57%   -0.04%     
==========================================
  Files         649      649              
  Lines       87048    87048              
==========================================
- Hits        44923    44894      -29     
- Misses      39263    39284      +21     
- Partials     2862     2870       +8     

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