Implement ISpanParsable<Version> on System.Version

[SkyDevLab]

Fixes #125026

Customer Impact

As approved in API review #125026, System.Version previously implemented IUtf8SpanParsable, but not ISpanParsable (nor IParsable).
This PR implements ISpanParsable (and by extension IParsable) explicitly on System.Version.

Proposed Changes

1. System.Private.CoreLib (src/libraries/System.Private.CoreLib/src/System/Version.cs):
   • Added ISpanParsable to the interface implementation list on System.Version.
   • Added explicit interface implementations for:
     • static Version IParsable.Parse(string s, IFormatProvider? provider)
     • static bool IParsable.TryParse([NotNullWhen(true)] string? s, IFormatProvider? provider, [NotNullWhen(true)] out Version? result)
     • static Version ISpanParsable.Parse(ReadOnlySpan s, IFormatProvider? provider)
     • static bool ISpanParsable.TryParse(ReadOnlySpan s, IFormatProvider? provider, [NotNullWhen(true)] out Version? result)
   • Factored common contract parsing validation through a shared ParseHelper routine (matching the existing IUtf8SpanParsable.Parse error semantics to ensure FormatException is thrown on invalid inputs).
2. System.Runtime Ref Assembly (src/libraries/System.Runtime/ref/System.Runtime.cs):
   • Added IParsable<System.Version> and ISpanParsable<System.Version> to System.Version interface list and declared the explicit interface methods.
3. Unit Tests (src/libraries/System.Runtime/tests/System.Runtime.Tests/System/VersionTests.cs):
   • Added comprehensive tests for generic IParsable and ISpanParsable parsing, null input validation, invalid input formatting exceptions, and trailing dot edge cases.

Validation

• System.Private.CoreLib.csproj builds cleanly (0 warnings, 0 errors).
• System.Runtime/ref/System.Runtime.csproj builds cleanly (0 warnings, 0 errors).
• System.Runtime.Tests.csproj compiles cleanly with the new test suite referencing the updated contracts.
• Formatting verified clean with git diff --check.

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[lilinus]

nit: these are already available in ParsableHelper, SpanParsableHelper and Utf8SpanParsableHelper.

[SkyDevLab]

Updated to use the shared ParsableHelper<T>, SpanParsableHelper<T>, and Utf8SpanParsableHelper<T> test classes in commit 4c30ddb. Thanks!

[lilinus]

Unintentional BOM change (removal)? I believe this should be reverted.

[SkyDevLab]

Restored the UTF-8 BOM on Version.cs in commit 4c30ddb. Thanks!