Remove 250MB of gc generated by delegate allocations during OOP synchronization.

kill build processes before perf run ALSO fail build if we can't kill build processes

Fixes #15238

	Add ability for callback to specify a message to display to the user.

Extract out helper code to a common location.

Find usages - move files

This PR implements completion for the simple cases of async and void in
a local function context. What it misses cases where parsing incorrectly
considers bare modifiers to be local variable declaration statements
rather than local function declaration statements. This is tracked by
bug #14525.

Fixes #8616
Fixes #8617

Pass around an interface so clients don't have access to anyth ing they shouldn't have.

Present go-to-implementation results in the new Streaming FindRefs window if there are multiple results.

Remove interfaces used for temporary prototype

	Move UseObjectInitializer over to the new FixAll system.

Only repeat IO if we actually failed performing the operation.

Rename internal code to 'FindUsages' so it better reflects that it can present results for more than just FindReferences.

Rename intenral code to 'FindUsages' so it better reflects that it can present results for more than just FindReferences.

Call into all CompletionProviders in parallel to speed up completion.