Restore the LogEntry based SaveLogs signature

[jhonabreul]

Description

PR #9632 split BaseResultsHandler.SaveLogs into two overloads (List<LogEntry> and IEnumerable<string>) so BacktestingResultHandler.Exit() could reuse the message-list clone. This restores the original public API:

• BaseResultsHandler.SaveLogs(string id, List<LogEntry> logs) is again the single overload, writing the entry messages itself.
• BacktestingResultHandler.Exit() clones the LogEntry list under the log store lock and passes it to SaveLogs, as it did before Run a reduced results analysis periodically during backtests #9632.
• CloneLogs() stays for the final-result and in-run analysis paths, which need the message strings.

Related Issue

N/A

Motivation and Context

SaveLogs is a public virtual member that result handler implementations override; its signature should not have changed as a side effect of #9632.

Requires Documentation Change

N/A

How Has This Been Tested?

• BaseResultsHandlerTests, BacktestingResultHandlerTests and LiveTradingResultHandlerTests: 31 passed.
• Manual Launcher run of an algorithm logging on every bar: BacktestingResultHandler.Exit() saved the complete log file (launch line, 390 bar lines, end-of-algorithm line, completion line) at the end of the backtest.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Refactor (non-breaking change which improves implementation)
• Performance (non-breaking change which improves performance. Please add associated performance test and results)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Non-functional change (xml comments/documentation/etc)

Checklist:

• My code follows the code style of this project.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes (no new tests: restores the pre-Run a reduced results analysis periodically during backtests #9632 signature, already covered by the existing result handler fixtures).
• All new and existing tests passed.
• My branch follows the naming convention bug-<issue#>-<description> or feature-<issue#>-<description>