Remove benchmarks and use .NET9 SDK

[jnyrup]

The motivation for this PR was to reduce the number of dependabot PRs by removing dependencies on Bogus and BenchmarkDotNet

The update to use .NET9 SDK was because I didn't have .NET8 SDK installed locally.

IMPORTANT

• If the PR touches the public API, the changes have been approved in a separate issue with the "api-approved" label.
• The code complies with the Coding Guidelines for C#.
• The changes are covered by unit tests which follow the Arrange-Act-Assert syntax and the naming conventions such as is used in these tests.
• If the PR changes the public API the changes needs to be included by running AcceptApiChanges.ps1 or AcceptApiChanges.sh.