* moved waiter from diagnostics.dll to features.dll where all interfaces are defined.

* simplified listener and waiter and moved those in product.

* cleaned up a bit

* fixed some comments

* forgot to add new AsyncListenerProvider in test export composition

* fixed dead lock found on unit tests

* remove all waiters left

* added dispatcher event processing in one more place

* added a way to enable waiter through env variable in test such as DDRIT

* added env var support so that It can be used without internalvisibleTo us.

* dont wait for all waiters but only onces each test used to wait.

* removed dependency to Roslyn.Services.Test.Utilities in integration test. that dll is not in probing path.

* fixed test failures

* fixed bug in integration tests

* move call to enable waiter before creating workspace so that workspace event queue get proper async listener

* expose concret type as well so that it can be directly used in test for waiter

* addressed PR feedbacks.

* rename mess up

* extra ) left out

* fixed build failure

* Simplify diagnostic tagging by making it use the standard tagging model.

* Cleanup.

This centralizes the logic for detecting the language of the tmp_proj
files that are generated during WPF compilation.

Closes #23479

The QuickInfoDisplayDeferredContent type was somewhat evil: it had a
set of properties that were intended as test-only accessors, that would
give you access to fields of type IDeferredQuickInfoContent but would
cast to the expected concrete type. In a previous refactoring I
started using those properties in the product which breaks F# because it may
create different implementations from IDeferredQuickInfoContent.

My fix here is just to delete the properties and clean up the test
helpers to do explicit casting. By refactoring the helpers a bit the
test complexity doesn't change and eliminates the trap in the first
place.

The new ILSpy functionality will be driven by the existing Go To Definition command.

This takes care of Microsoft.VisualStudio.Imaging and
Microsoft.VisualStudio.ImageCatalog, which for now aren't available
outside Visual Studio. ImageCatalog is a pretty simple data API so
one day it might be useful, but for now isn't.

Fixes dotnet/roslyn#23189.

Moving up to EditorFeatures.Wpf for now. It could potentially go higher
if we determine this is a Visual Studio-only thing, but for now it's
unclear where it will ultimately land.

Fixes dotnet/roslyn#23184.

This depends on VS APIs that we don't have open source yet, and we
don't need the feature for now in VS for Mac.

Fixes dotnet/roslyn#23192.

The trim_trailing_whitespace can affect tokens to the right of the caret
so we need to check the token to the left.

This lets us remove many stated dependencies on
Microsoft.VisualStudio.Text.Internal and dependency on
Microsoft.VisualStudio.Platform.VSEditor.Interop. Both
is a stated dependency of Microsoft.VisualStudio.Platform.VSEditor
which means we don't get any benefit for trying to state it -- and it's
actually hard since it has a different version anyways.

* added time tracking to completion set.

from the point we start completion set to first time we are called from VS for best match (which indicate that completion set is actually shown to users first time for this particular completion session)

the event is vs/ide/vbcs/intellisense/completion

if completion is done without showing UI to users (etc or tab), then event will be marked as cancelled.

* added perf tracking to LB fix all.

there were already existing events so I just made those to include perf info (duration) as well.

among all those events, these 2 are ones we were planning to add

vs/ide/vbcs/codefixes/fixalloccurrencescomputation
this shows time from the point user invoked fix all to where we shows preview window to users.

vs/ide/vbcs/codefixes/applychanges
this shows time from user clicked Apply from preview window to where we actually applied the changes to VS

there are more events between them in case we want to dig in details later such as how long it took to calculate diagnostics, how many files are affected and etc.

also all related events have correlation id to group related code fix events. also for fix all case, it contains scope to show whether fix all is for document, project, solution.

* PR feedback. removed unnecessary parameter

* removed repeated correction id set

* updated comments.

It wasn't even being used. :-(

looks like I broke it when I did refactoring on KeepAliveSession by giving in wrong callback object.

fix https://github.com/dotnet/roslyn/issues/22806

opened this for adding unit test - https://github.com/dotnet/roslyn/issues/22808

currently we don't have test around ISymbolSearchService.