Make the default suggested action behavior to not show a preview.  Only override that for fixes/refactoring.

This is necessary so that the light-bulb will dismiss with long running
suggested actions.  Otherwise, it will stick on the screen for the duration
of 'Invoke()'.

Note: integration tests already do a 'wait' after invoking to make sure
the light bulbs have finished.  So they are unaffected by this.

This change adds a new code action to Features layer Suppression fixer to enable Removing suppressions on diagnostics which are suppressed in source by pragma/SuppressMessageAttribute. Additionally, this change also adds a batch fixer to enable removing suppression on multiple/all diagnostics. This functionality will be consumed by the "Remove suppression(s)" context menu for error list selection.

Put generate-type actions under a higher level "Generate Type" menu item if there are a lot of items in the code actions list.
If there aren't a lot of actions, then inline the items.
Simplify the wording of the "Generate type" actions to make the menu items cleaner.
Provide simple APIs to allow users to create top level menu actions with sub actions.

1. CompilationWithAnalyzers can now report analyzer diagnostics with source suppressions (pragma/SuppressMessageAttribute). This will eventually allow us to surface diagnostics with source suppressions in the error list. Note that the behavior of command line compilers and all the GetDiagnostics APIs is unchanged, only the compiler analyzer will report diagnostics with source suppressions.

2. Add FixAll support for Suppression code fixes. Light bulb suppression fixes now show the "Fix all occurrences" options for Document/Project/Solution. This change adds the basic functionality to bulk suppress diagnostics. This will eventually be consumed for baselining all/selected diagnostics from error list/solution explorer.

3. Simplify the Suppression light bulb menu to remove the option to add a local SuppressMessageAttribute. The only options now are to suppress in source (pragma) or suppressions file (assembly level SuppressMessageAttribute).

Consume new async light bulb APIs. This makes the light bulb preview pane render asynchronously so that expensive previews don't block the UI thread.