This patch is the second part in a patch series that will allow
enabling/disabling InstrumentationRuntime plugins in a running debug
session.
This patch contains a set of NFC changes that will be needed when
implementing support for enabling/disabling InstrumentationRuntime
plugins in the `debugger` and `target` domains.
In particular
* In several places the `PluginManager` was modified to get access to
information about disabled plugins. Previously interfaces would only
return information about enabled plugins.
* `InstrumentationRuntimeInstances` is now struct rather than a typedef
so it can contain a helper method that allows looking up a
`InstrumentationRuntimeGetType` callback based on the plugin name. This
is very similar to the existing `PluginsInstances::GetCallbackForName`
method.
rdar://167725878
4adcde983b