.NET 9 code quality fixes

[voldemort2826]

Reopen for #682 due to branch name change

Address code quality checks introduced in .NET 9. Easiest one like "name/collection initialization can be simplified" are fixed automatically with Visual Studio.

Todo

Level: easy

• Address CA2201: Exception type System.Exception is not sufficiently specific (commit f084711)
• Silence/ignore unnecessary warnings
• Address rest of the warnings before moving on to the <AnalysisMode>Recommended</AnalysisMode>
• Use ReadyToRun publishing instead of NativeAOT because third-party libraries produced trim warnings
• Remove custom ChaCha20 implementation in favor of Sodium.Core [require testing with real ChaCha20 stream, but it's rare]

Level: medium

• Address additional warnings by <AnalysisMode>Recommended</AnalysisMode>