In recent dogfood VS builds we've gotten many IDE0251 suggestions, some warnings escalated to errors in StringTools. Follow many of those suggestions, but bump the rule down to suggestion always, like the related IDE0250.
IDE0055 is currently too unspecific - opting out of it.
### Sample error:
```
C:\src\msbuild\src\Build.UnitTests\BackEnd\MSBuild_Tests.cs(796,59): error IDE0055: Fix formatting [C:\src\msbuild\src\Buil
d.UnitTests\Microsoft.Build.Engine.UnitTests.csproj::TargetFramework=net472]
```
(changed to message and not blocking the build after this change)
Context
Types that are not designed to be inherited from should be sealed. This is general defensive goodness, and also has perf implications because it enables some runtime/JIT optimizations. A new analyzer was recently added for this.
Changes Made
Enabled the analyzer and fixed the code with dotnet format.
Testing
Manual review of the changes.
Notes
dotnet format also rectified our namespace imports. I don't believe there's any controversy in that and the change is low risk so I left it in. For the actual sealing:
It missed one class because it was ifdefed out in Core. I fixed it manually.
It resulted in a handful of build errors where the compiler didn't like protected members in sealed types. I fixed those manually.
The analyzer doesn't understand InternalsVisibleTo, by design. This is not causing any issues for us now as we don't derive from internal types in other assemblies. Our InternalsVisibleTo all point to our own assemblies built in this repo so this is a non-breaking change (unless hacks, reflection, etc. but the bar is certainly not that high).
I am not including changes to files under src/Deprecated in this PR.
* added IDE code style checks as warning, set the currently violated rules to suggestion
* auto-fixed IDE0011 - add braces to statement
* auto-fixed IDE0036 - Modifiers are not ordered
* auto fixed IDE0040 - Accessibility modifiers required
* auto-fixed IDE0055 - fix formatting
* auto-fixed SA1110 and SA1111 - parenthesis formatting
manually fixed unresolvable cases
* auto-fixed IDE0073 - A source file contains a header that does not match the required text
* moved IDE rules to .editorconfig as they need to be filtered
* added IDE0020 - use pattern matching to be excluded
* extra disable format due to chunk of code conditioned for DEBUG only
* added comment in Version line to bypass the check
clarified CTA on how to bypass the error
* extra disable format due to chunk of code conditioned for DEBUG only
Rainer Sigwald
Jan Krivanek
Ladi Prosek
Vlada Shubina
Lachlan Ennis
Paul Vick
Yannis Güdel