Add Configure severity code action to enable configuring severity of diagnostics using .editorconfig files (analyzer config documents)

Introduce a new, deterministic BatchFix application algorithm. The new algorithm works in the following manner:

When producing code-actions, we keep track of both the code-action and the diagnostic that was used to create it. When we later go and 'apply' the code actions in a single document, we'll process them in diagnostic-location order. Is is as if we took each diagnostic of a document in order, produced the CodeAction for that diagnostic, and then applied that CodeAction.

I also took this opportunity to clean up and parallelize much of this code. We now compute code actions in parallel, and we process all documents in parallel when applying changes. Once all application is done, we can then take all the final results and apply them to the solution.

Only pass FixAllContexts to methods that actuall y need it.  For internal methods that don't need all that functionality, pass a FixAllState instead.

Fix a few issues related to trivia generation for add/remove suppression fixes from the error list. Unit tests have been added for the same.

Add support for adding/removing suppressions for diagnostics with no source location. Additionally,  when the diagnostics being suppressed or unsuppressed are across different languages, instead of showing a preview changes dialog per-language, we now show a single preview changes dialog for the entire changed solution.

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.