Update Roslyn to 3.5.0-beta2-19606-01

[JoeRobich]

Updates to a 16.5 Preview2 build of roslyn

Changes from fb3f812 to e8ab154:

View Complete Diff of Changes

• More tests for [MaybeNull] (39983)
• Nullable collections (40029)
• Make finding checksum async (40091)
• Fix AllowNull/DisallowNull in object initializers (40127)
• Convert operand expressions in an error case (40093)
• Remove the nullable wrappers from the Workspaces layer (40030)
• Diagnostics refactoring (40078)
• Implicit numeric casts shouldn't be recommended to be removed if doing so loses precision (39543)
• Prefer user-defined conversion over a switch expression conversion (39953)
• Store nested conversion in the target-typed switch expression conversion (40107)
• Remove diagnostics from error list on document close or reset for tha… (39892)
• Update list of C# Next features and reviewers (39987)
• Add code action to extract local functions (39745)
• Fix for configuring code style for "infer member names in anonymous types" persists the wrong setting (40017)
• Always restore when running a bootstrap build (40025)
• DiagnosticIncrementalAnalyzer refactoring (39956)
• Simplify how we compute and store the location we use to persist the sqlite storage cache. (39655)
• Move LiveShare off of the deprecated constructors and project shims (39938)
• Move reporting of iterator diagnostics to avoid race condition (39990)
• Fix NGEN priority of csc.exe, vbc.exe, csi.exe (40016)
• Extra check for EnumeratorCancellation parameter type (39978)
• Extend profiling inputs drop time to 90 days (40009)
• Change to telemetry logger (39982)
• Emit CS8370 instead of CS1674 for ref struct disposable (39949)
• Move the ClosedFileDiagnostic option used by TS back to Features layer (39980)
• Do not convert PDBs when building bootstrap compiler (39972)
• Ensure that work coordinator sees change to "RunAnalyzers" project pr… (39973)
• Avoid warning assigning to readonly property marked [AllowNull] (39939)
• Properly respect 'var' settings when generating equals/GetHashCode (39958)
• Update FormattingDiagnosticIds.cs (39957)
• Re-add ServiceFeatureOnOffOptions.ClosedFileDiagnostic to fix the bre… (39955)
• Improvement for completion of unimported types (39813)
• Decouple command filters and contained documents from language service (39910)
• Track additional state for "maybe null even if not nullable" (39778)
• Address a number of variance safety issues with code in interfaces. (39839)
• Cleanup hoisted locals at async state machine end (#34239) (39735)
• Add "Active file" analysis scope for background analysis in the IDE (39699)
• Add new feature to switch existing interface impl to/from implicit/explicit impls. (39756)
• Fix assertion failure in CFG-builder (39866)
• Filter optprof to specific tests (35700)
• Fix so move to namespace also works for enums when selected (39798)
• Remove capturing lambdas from the language parser. (39829)
• Disable the goldbar for suggesting install of FxCop analyzers (39819)
• Cleanup hoisted locals at async state machine end (34239)

[filipw]

there are some test failures around the available code actions

[JoeRobich]

@filipw Thanks. Updated the tests.