Fix compliance findings in Frends.ServiceBus.Read

[Copilot]

Resolves 6 analyzer findings (FT0011, FT0014, FT0015) and upgrades target framework from net6.0 to net8.0.

Breaking changes (version → 2.1.0)

• Result class now includes Success (bool) and Error properties per FT0011. Existing Results list property preserved.
• New Error class (Message, AdditionalInfo) added to Definitions/.

Error handling

• Options gains required ThrowErrorOnFailure and ErrorMessageOnFailure properties (FT0015), defaulting to true and "" respectively.
• ErrorHandler and ValidationHandler added to Helpers/, matching the platform-standard pattern.
• Read() body wrapped in try/catch delegating to ex.Handle(options):

catch (Exception ex)
{
    return ex.Handle(options);
}

Analyzer / framework setup

• Target framework → net8.0 (both main and test projects)
• Added StyleCop.Analyzers, FrendsTaskAnalyzers package references
• Added GlobalSuppressions.cs and AdditionalFiles for FrendsTaskMetadata.json
• Added missing <example> XML doc tags on MessagingFactory.Instance and Result.Results (FT0014)

Tests

• ErrorHandlerTests.cs: 3 MSTest cases covering throw-on-failure, return-failed-result, and custom error message scenarios using an invalid connection string to trigger failures.