The IndicesModule was made up of two submodules, one which
handled registering queries, and the other for registering
hunspell dictionaries. This change moves those into
IndicesModule. It also adds a new extension point type,
InstanceMap. This is simply a Map<K,V>, where K and V are
actual objects, not classes like most other extension points.
I also added a test method to help testing instance map extensions.
This was particularly painful because of how guice binds the key
and value as separate bindings, and then reconstitutes them
into a Map at injection time. In order to gain access to the
object which links the key and value, I had to tweak our
guice copy to not use an anonymous inner class for the Provider.
Note that I also renamed the existing extension point types, since
they were very redundant. For example, ExtensionPoint.MapExtensionPoint
is now ExtensionPoint.ClassMap.
See #12783.
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