Large refactor, Code Simplification

[james7132]

• Added simplified methods to reduce boilerplate request code on WebAgent
• Removed WebAgent function parameters where Reddit instances are already being passed.
• Removed public setters on a most entities that shouldn't
• Changed deserialization to use JsonSerializer.PopulateObject instead of JsonConvert.PopulateObject. Should have positive performance benefits due to avoiding dumping to strings.
• Use more more modern C# syntax to simplify code.
• Switch to using LINQ in areas where it would make code more readable.
• Removed project.lock.json, since it's autogenerated.
• Moved duplicated code within Init/InitAsync functions into constructors.
• Added ConfigureAwait to all awaited functions.

[CrustyJew]

This is awesome! Hadn't considered the public setters issue, but you are totally right, they shouldn't have been on half the stuff that was there. Really like the simplified constructors and everything.

This does tie in to some of the discussion #40 so some of the changes to LINQ may be a bit irrelevant, but could just get moved to a method body instead as it's still "cleaner" in my opinion.

Merging this in and I'll push another pre-release to NuGet. I'd like to address a couple of the discussions (#40, #42) then we can probably release a Beta for 2.0.0 I've been using the pre-release version in some bot code without issues so far, so I'm excited to see how these changes merge in.

Closes #41