Fix flaky CleanBackup test: use version-based sorting instead of CreationTime

[JusterZhu]

Closes #395

Summary

Fixes 4 pre-existing test failures that were excluded from CI:

Test	Root Cause	Fix
\CleanBackup_KeepsOnlyRecentVersions\	Sorting by \CreationTime\ — non-deterministic when dirs created in quick succession	Sort by \Version.TryParse\ on directory name
\Build_InitializesCollectionProperties\	\ConfiginfoBuilder.Build()\ doesn't default null collection fields	Add ?? new List<string>()\ for BlackFiles, BlackFormats, SkipDirectorys
\SharedMemoryProvider_RoundTrip\	\SendAsync\ disposes MMF before \ReceiveAsync\ can open it	Use \CreateOrOpen\ + hold MMF reference in field
\AutoProvider_ThrowsWhenAllFail\	\SendAsync\ providers don't respect CancellationToken; test used delayed token instead of pre-cancelled	Add \ oken.ThrowIfCancellationRequested()\ to SendAsync; use \
ew CancellationToken(true)\ in test

Verification

Full CoreTest suite: 259/259 pass, 0 failures (previously 4 failures)

[Copilot]

Pull request overview

This PR addresses flakiness in StorageManager.CleanBackup by making backup-retention deterministic: instead of sorting backup directories by filesystem CreationTime, it sorts by the version encoded in the directory name.

Changes:

• Replace CreationTime-based ordering in StorageManager.CleanBackup with ordering derived from Version.TryParse(directoryName).
• Keep the “retain N most recent, delete the rest” behavior unchanged, but make the ordering deterministic for rapidly-created directories.

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