Major refactoring of tests and benchmarks

[michelebastione]

Tests

• Removed superfluous packages (FluentAssertions, ClosedXml.Report, NSubstitute) and updated remaining packages
• Optimized import sattements
• Synced namespaces to MiniExcelLibs.Tests and changed block scopes to file scopes
• Extensive use of collection expresions and using statements
• Changed Console.WriteLine calls to ITestOutputHelper.WriteLine
• Added AutoDeletingPath helper class to avoid having to manually delete temp files at the end of every method
• General code cleanup and styling for simplicity and readability

Benchmarks

• Updated packages and target frameworks to have a more modern and realistic comparison with other libraries
• Added AutoDeletingPath helper class to avoid having to manually delete temp files at the end of every method
• Changed Program.cs file to top level statement syntax
• Code cleanup

Other

• Minor change to template regex
• Made some exception messages clearer
• General code cleanup

[michelebastione]

I know this is a lot of code changes but most of it is just about styling and formatting

[shps951023]

❤❤ I had an issue before : because I don't know how to get maximum memory usage (not total memory usage) by dotnet benchmark. so the issue not finished yet.

[michelebastione]

I'm afraid that's not going to be possible with benchmarkdotnet, that information is not registered anywhere.