Opening the Run Configurations dialog with a JUnit launch config can be slow

see: https://github.com/groovy/groovy-eclipse/issues/1659

When opening the Run Configurations dialog, the `TestSearchEngine` kicks in -- presumably to populate this group of controls:

**1)** Is it possible to defer searching for test methods until the _Search..._ button is pressed?

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For any test type with a super class or super interface(s) there is an expensive computation:
https://github.com/eclipse-jdt/eclipse.jdt.ui/blob/9d72b01bc21e7aa44269514b09db3d8d05725ffb/org.eclipse.jdt.junit/src/org/eclipse/jdt/internal/junit/util/TestSearchEngine.java#L92

It is costly to look up a type name within the context of a source unit, using `getResolvedType` -- it requires a full parse and resolve that is discarded.

**2)** Would it be better to use `ITypeHierarchy superTypes = type.newSupertypeHierarchy(subMonitor.split(1));` to compute the entire type hierarchy, which could then be iterated for test method discovery?

@kernanj

Start by reading eclipse.jdt.ui's org/eclipse/jdt/internal/junit/util/TestSearchEngine.java around line 92 and tracing how the Run Configurations dialog invokes it. Reproduce the slow JUnit launch-configuration workflow, measure dialog opening and test search separately, and use the findings to define the accepted behavior and regression coverage.

Written by the indexing model from the issue text.