refactor: remove ledgercore.OnlineAccountData

[algorandskiy]

Summary

Use basics.OnlineAccountData instead since they are exact duplicates.

Test Plan

Existing tests.

Notes

Merge after #5757 due to conflicts

[codecov]

Codecov Report

Attention: Patch coverage is 48.14815% with 14 lines in your changes are missing coverage. Please review.

Project coverage is 56.18%. Comparing base (d99c5c3) to head (09e05a5).
Report is 1 commits behind head on master.

Files	Patch %	Lines
ledger/ledgercore/accountdata.go	14.28%	6 Missing ⚠️
ledger/acctonline.go	60.00%	4 Missing ⚠️
...r/store/trackerdb/generickv/accounts_ext_reader.go	0.00%	2 Missing ⚠️
ledger/store/trackerdb/sqlitedriver/accountsV2.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5965      +/-   ##
==========================================
+ Coverage   55.93%   56.18%   +0.25%     
==========================================
  Files         482      482              
  Lines       67969    67949      -20     
==========================================
+ Hits        38019    38178     +159     
+ Misses      27343    27178     -165     
+ Partials     2607     2593      -14     

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[jannotti]

I think this is mergable now. Thanks for waiting on the incentives PR.

[cce]

They're not exact duplicates, I just noticed, because basics.OnlineAccountData has LastHeartbeat/LastProposed, but ledgercore.OnlineAccountData did not have it. So there are some conversion functions that didn't set LastHeartbeat/LastProposed on ledgercore.OnlineAccountData, because it didn't have these fields, but were leaving them empty on conversions from e.g. basics.AccountData => basics.OnlineAccountData because of this change ... addressing this in #6085