SemanticModel should cache synthesized bound statements in a separate cache in order to avoid “polluting” regular cache. (#18662)

Fixes #10604.
Fixes #16306.

Fixes #17921

Ensure proper handling of a line-break following an incomplete string interpolation.

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems?id=405887.
The error recovery wasn’t including the line-break into interpolated string, yet wasn’t creating proper statement terminator token for it. The change ensures that the line-break is treated as part of the string for the purpose of the error recovery, this is what would happen if the interpolation was properly terminated with ‘}’ before the end of the line.

Fixes #18188

Removes control type from NavBar's accessible names

Report an NFW instead of asserting when we encounter a symbol we can't roundtrip to OOP.

Don't offer to convert an 'if' to a 'throw expressoin' if there is an 'else clause'

Add back the PR template.

Include default in 'Compiler Test Plan.md'

This change fixes two problems in our powershell scripts

1. Removes all uses of Invoke-Expression.  This commandlet doesn't do error checking on windows
commands and hence can hide failures.  Relpaced with Exec-Expression which properly checks
both the windows command error and the powershell error
1. Reset $LastExitCode inside Exec before executing the script block.  This avoids cases where
previous windows command failures could carry over to a script block that didn't execute any
windows commands.

Powershell guidelines changed appropriately

https://github.com/dotnet/roslyn/blob/master/docs/contributing/Powershell%20Guidelines.md

Fix extract method test baseline

Fix CsharpCodeActions.FastDoubleInvoke flakiness

Do not fully qualify type name if it would not resolve error.

Classify type names, even when arity does not match.

Port BasicEndConstruct

Fix crash in implements clause completion