feat: align all components to SemVer 2.0 for version comparison

[JusterZhu]

Problem

The GeneralUpdate SDK uses System.Version (Version.TryParse, new Version(string)) for all version comparison logic across Core, Extension, and Drivelution components. System.Version does not support SemVer 2.0 — it rejects prerelease suffixes (e.g. "10.5.0-beta.2") and build metadata, causing either silent "no update needed" (returning false from TryParse) or a FormatException (from new Version()).

Since all NuGet packages are already versioned as 10.5.0-beta.2 (valid SemVer 2.0), this means a client configured with version "10.5.0-beta.2" would never see an update — the comparison silently skips.

Solution

Replace all System.Version usage with a dedicated Semver utility class that follows SemVer 2.0, aligned with the existing implementation in GeneralUpdate.Infrastructure.Common/Utilitys/Semver.cs.

Changes

New files

• src/c#/GeneralUpdate.Core/Utilities/Semver.cs — SemVer 2.0 validation, parsing, comparison, normalization
• src/c#/GeneralUpdate.Extension/Utilities/Semver.cs — Same, for Extension (netstandard2.0 compatible)
• src/c#/GeneralUpdate.Drivelution/Core/Utilities/Semver.cs — Same, for Drivelution

Modified files (Core)

• Download/DownloadPlanBuilder.cs — ParseVersion() now returns SemVersion?, all operators use SemVer 2.0 ordering
• Strategy/OssStrategy.cs — Replaced new Version() + Version.TryParse with Semver.TryParse
• Strategy/ClientStrategy.cs — CheckFail() uses Semver.TryParse
• Configuration/UpdateConfiguration.cs — Default ClientVersion from "1.0.0.0" → "1.0.0"

Modified files (Extension)

• Compatibility/VersionCompatibilityChecker.cs — All Version.TryParse + </> → Semver.TryParse + SemVersion operators

Modified files (Drivelution)

• Core/Utilities/VersionComparer.cs — Marked [Obsolete], delegates to Semver

Tests

• CoreTest/Configuration/UpdateConfigurationTests.cs — Assert "1.0.0" instead of "1.0.0.0"
• DrivelutionTest/Utilities/VersionComparerAndRestartHelperTests.cs — Updated for aligned Semver

Bugs fixed incidentally

1. CVP matching never worked: Old code used fromVer == localVersion on nullable System.Version (reference type without == overload → always false)
2. OssStrategy NPE: assets.Max()!.Value on an empty parsed-collection would NPE — added guard

Backward compatibility

• Legacy 4-part versions (e.g. "1.0.0.0") are accepted and normalized to "1.0.0"
• HasUpdate() still returns true when version is unparseable ("safe side" policy)
• All existing SemVer 3-part comparisons produce identical results
• Drivelution VersionComparer is preserved as an [Obsolete] delegate

Breaking changes

• 4-part version fourth segment is discarded (required by SemVer 2.0)
• Drivelution VersionComparer no longer throws FormatException on invalid input (returns 0 instead)
• Version numbers exceeding int.MaxValue (~2.1e9) are treated as invalid