Add code folding support for records.

Update configs

Merge 16.9p1 into master

Merge master to release/dev16.9-preview1

Merge release/dev16.8 to master

Fix for generate constructor naming bug

Fix VB invert single line code fix crash

Add UnmanagedCallersOnly runtime testing

Merge release/dev16.8 to master

Avoid cancellation exceptions when possible for expedited waits

Use GetTextSynchronously where appropriate

Ensure IServiceBroker is used on a background thread

* Records: Warn if Equals or GetHashCode is redefined, but not both

* Fix ErrorFacts.Generated.cs

* Apply feedback from @jcouv

* Fix RecordTests.cs due to new warnings - part 1

* Small fix

* Small fixes

* Fix RecordTests.cs due to new warning - part 2

* Fix formatting

* Fix RecodTests.cs due to new warning - part 3

* Fix RecodTests.cs due to new warning - part 4

* Fix RecodTests.cs due to new warning - part 5

* Fix RecodTests.cs due to new warning - part 6

* Fix an unintentional mistake

* Apply feedback

* Update src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs

* Apply feedback

* Feedback

* UpdateXlf

* Update DiagnosticTest.cs

* Update RecordTests.cs

* Update WarningLevel to 3

* Fix test: warning level

Fix synchronization of DesignTimeDocument

Merge master to release/dev16.9-preview1

We don't have .NET 5 ref assemblies yet, so I can't remove the override flags/custom definition of UnmanagedCallersOnlyAttribute. But when running on CoreCLR, everything does work when overriding our error, so I'm now testing that. As part of this, I rewrote the existing Thiscall tests to use pure C#, instead of a ton of IL. This was a line-by-line port of the existing IL. I then wrote a UnmanagedCallersOnly equivalent of the simple Thiscall case. While I did convert ThiscallBlittable to pure C#, I don't believe that it exercises anything different from a C# perspective so I didn't add an UnmanagedCallersOnly version of it.

Sort the code fix action for UnusedValueCodeFixProvider

Implement UnmanagedCallersOnly conversions support

* Issue a warning when a global analyzer config contains an invalid section name.

Result of << operator for native integer constants is platform-dependent in unchecked context (#47881)

* Enable automatic discovery of global editor configs
* Split out editor/global config discovery for ease of addition.
* Account for other editorconfigs in tests

Don't rename the file if the replacement text is invalid

* Simplified convention type checking
* Fixed stackoverflow in attribute constructor overload resolution
* Added more loop tests.

A copy constructor shouldn't prevent an automatic addition of a default instance constructor for a record. (#47850)

https://github.com/dotnet/csharplang/pull/3913

* Don't offer to fix naming on positional record parameters

* Nullable enable

* Fix formatting

* Fix issue with nested constructors and parameters

* Rebase and remove ThrowIfNull