[PS-40] Upgrade to .NET 6 (#2056)

* Bump to .NET 6

* Update Docker images

* Update docs

* Update workflow for linter

* Add all common versions to props file

* Update tools manifest

* Update csproj files

* Update packages.lock.json files

* Switch to setup-dotnet

* Remove msbuild

* Fix deps breaking changes

* Manually install msbuild

* Use msbuild for build

* Fix verbosity switch

* Remove unused exceptions

* Address linter feedback

* Make Obsolete warnings suggestions for now.

* Force Evaluate

* Format on tests

* Run formatting again.

* Use windows 2022

* force evaluate

* Fix restore

* Fix linter

* Skip test

* Update Directory.Build.props

Co-authored-by: Matt Gibson <mgibson@bitwarden.com>

* Address PR feedback

* Add IntegationTest for Rate limiter

* Fix test

* Reenable test

* Reorder test

* Skip test again

* Add tracking link

* Update .github/workflows/build.yml

Co-authored-by: Micaiah Martin <77340197+mimartin12@users.noreply.github.com>

Co-authored-by: Matt Gibson <mgibson@bitwarden.com>
Co-authored-by: Micaiah Martin <77340197+mimartin12@users.noreply.github.com>

test/Core.Test/Services/SendServiceTests.cs

@@ -495,8 +495,6 @@ namespace Bit.Core.Test.Services
             send.UserId = user.Id;
             send.Type = SendType.File;
 
-            var testUrl = "https://test.com/";
-
             sutProvider.GetDependency<IUserRepository>()
                 .GetByIdAsync(user.Id)
                 .Returns(user);