VSTHRD103 reminds people not to use .Result in tasks, which is great
advice but we get a few false positives; in particular our
SafeContinueWith extension isn't understood by the analyzer that the
tasks involved are always completed, so you can just .Result them.
Rather than working around this, let's just disable the analyzer in
those cases.

Fixes
https://devdiv.visualstudio.com/DevDiv/_workitems?_a=edit&id=371205

Fixes #14159

The well-known ValueTuple types are very special in that you can ask for
the SymbolInfo on the ValueTuple token and not get back the ValueTuple
type. This means that the token we invoke rename on has no locations,
which Rename Tracking mistakenly interpreted as being okay to rename.
This has been fixed, and also the RenameUtilities.GetTokenRenameInfo
method has been updated to return NoSymbolsTokenInfo when it finds an
ITypeSymbol with IsTupleType.

More CR feedback

Fixes #2605 "Lightbulb suggests renaming a type to 'var'"

This change disables using Rename Tracking to rename to/from "var" and "dynamic" in C#.

Fixes internal bug #762964

Rename tracking usually triggers the TrackingSessionUpdated event
whenever the buffer changes, except for buffer changes that occur before
the _isRenamableIdentifierTask completes. Prior to this change, rename
tracking would get stuck in its initial state between the completion of
_isRenamableIdentifierTask and the next buffer change. We now also
update the session when _isRenamableIdentifierTask completes.

This change adds support for renaming methods that are referenced in nameof expressions during Inline Rename, Rename Tracking, and RenameSymbolAsync. For all of these features, there are three primary cases:

- Rename invoked from a method declaration with no overloads: Any nameof expressions that reference the method are unambiguous and are therefore updated to the new name.
- Rename invoked from a method declaration with overloads: In this case, any references in nameof expressions are renamed only if the RenameOverloads option is set to true (e.g. when the user checks the "Rename overloads" checkbox in Inline Rename).
- Rename invoked from a reference in a nameof expression: We always rename all overloads by automatically setting the RenameOverloads option to true and disabling Inline Rename's "Rename overloads" checkbox.

In a handful of places, Task.FromResult(true), Task.FromResult(false), and Task.FromResult(default(T)) were being used, even though equivalent cached tasks are available in SpecializedTasks. This commit just changes those ~20 call sites to use already cached tasks.